user66400: I know it's not really a completely random selection because some miners have more hashing power so their odds are increased.
But let's assume for a moment that all miners are about equal in hashing power.
The way I see it, whoever solves the current block is (almost) completely unpredictable and thus mining is just a way to randomly select a winning miner.
I understand about decentralizing and the need for a decentralized way of selecting this winner without trusting a higher authority for this random selection.
Let's imagine for a moment that there was this "god-like" machine somewhere, completely trustworthy and incorruptible, impossible to bring down or shutdown and completely fair.
Let's say this machine would select the winning miner that would create and sign the next block and get the reward and fees.
Would there still be a need for mining in that case?

user49662: Mining adds a certain level of commitment to the process.
If mining were free, a corrupt user could create thousands or millions of corrupt miners (for free) that would publish invalid blocks that made itself rich, and try to get even one of these blocks accepted.
The same is true of your "god-like" random selector:
Publish blocks, and hope you get randomly selected!  
But mining is intensive: it costs money to setup a miner, and it costs electricity and networking to run a miner. You cannot fake thousands or millions of miners; each of them costs real money.
So the only way you can publish invalid blocks and hope to get rich is via a substantial investment.   The hash power of the network is so big now, that it is virtually impossible to setup a "evil" mining pool.  (If you succeeded, that would be a >51% attack)
The costs associated with mining ensure that there is a barrier to entry, and that "evil" miners cannot easily hope to overcome "honest" miners.  It ensures the integrity of the entire system.

user44137: Yes. You are not understanding the purpose of a miner.
Let us imagine this.
If someone wanted to broadcast a fraudulent transaction (Alice pays Bob 100 BTC without Alice's explicit approval), they would need to find the block before anyone else, place the fraudulent transaction in the block (very hypothetical), and broadcast the block to the rest of the network. Some people may accept this block, and some people may not depending on propagation time. At this point we will assume that due to conflict in block acceptance, there are two competing chains of blocks being mined simultaneously. If this malicious someone wanted to keep his/her blockchain authentic to all Bitcoin clients, he/she would need to find the following blocks before everyone else, again, each time. Bitcoin clients will, by default, trust the longest chain available to them. The chances of a malicious user finding all the blocks before everyone else until there are 6 confirmations on the malicious transactions is very unlikely.
3blue1brown has constructed a great, informative explanation to Bitcoin mining.

user9822: No, there wouldn't. The point of mining is to solve the consensus problem. Taking your logic further, if everybody believes in your god-machine, it might as well just clear the transactions itself.

66400: <p>I know it's not really a completely random selection because some miners have more hashing power so their odds are increased.</p>

<p>But let's assume for a moment that all miners are about equal in hashing power.</p>

<p>The way I see it, whoever solves the current block is (almost) completely unpredictable and thus mining is just a way to randomly select a winning miner.</p>

<p>I understand about decentralizing and the need for a decentralized way of selecting this winner without trusting a higher authority for this random selection.</p>

<p>Let's imagine for a moment that there was this "god-like" machine somewhere, completely trustworthy and incorruptible, impossible to bring down or shutdown and completely fair.
Let's say this machine would select the winning miner that would create and sign the next block and get the reward and fees.</p>

<p>Would there still be a need for mining in that case?</p>
 49662: <p>Mining adds a certain level of commitment to the process.</p>

<p>If mining were free, a corrupt user could create thousands or millions of corrupt miners (for free) that would publish invalid blocks that made itself rich, and try to get even one of these blocks accepted.</p>

<p>The same is true of your "god-like" random selector:<br>
Publish blocks, and hope you get randomly selected!  </p>

<p>But mining is intensive: it costs money to setup a miner, and it costs electricity and networking to run a miner. You cannot fake thousands or millions of miners; each of them costs real money.</p>

<p>So the only way you can publish invalid blocks and hope to get rich is via a substantial investment.   The hash power of the network is so big now, that it is virtually impossible to setup a "evil" mining pool.  <em>(If you succeeded, that would be a >51% attack)</em></p>

<p>The costs associated with mining ensure that there is a barrier to entry, and that "evil" miners cannot easily hope to overcome "honest" miners.  It ensures the integrity of the entire system.</p>
 44137: <p>Yes. You are not understanding the purpose of a miner.<br /><br />
Let us imagine this.<br /><br />
If someone wanted to broadcast a fraudulent transaction (Alice pays Bob <code>100 BTC</code> without Alice's explicit approval), they would need to find the block before anyone else, place the fraudulent transaction in the block (very hypothetical), and broadcast the block to the rest of the network. Some people may accept this block, and some people may not depending on propagation time. At this point we will assume that due to conflict in block acceptance, there are two competing chains of blocks being mined simultaneously. If this malicious someone wanted to keep his/her blockchain authentic to all Bitcoin clients, he/she would need to find the following blocks before everyone else, again, each time.<br/><br/> Bitcoin clients will, by default, trust the longest chain available to them. The chances of a malicious user finding all the blocks before everyone else until there are <code>6 confirmations</code> on the malicious transactions is <em>very</em> unlikely.<br /><br />
<a href="https://www.youtube.com/watch?v=bBC-nXj3Ng4" rel="nofollow noreferrer">3blue1brown has constructed a great, informative explanation to Bitcoin mining.</a></p>
 9822: <p>No, there wouldn't. The point of mining is to solve the <a href="https://en.wikipedia.org/wiki/Consensus_(computer_science)" rel="nofollow noreferrer">consensus problem</a>. Taking your logic further, if everybody believes in your god-machine, it might as well just clear the transactions itself.</p>
