user35795: At this point there are hundreds of Bitcoin wallets available https://bitcoin.org/en/choose-your-wallet
Clicking on a wallet reveals some areas where wallets are compared: 

Control
Validation
Transparency
Secure Environment
Privacy

Some excluded wallets are superior in some of these categories than the wallets listed. Is there a formal review process or criteria for wallet inclusion that someone can reference for me?

user5292: I don't know all the details, so if anyone has a better answer, please post it.
There are several volunteers that spend a lot of time reviewing and comparing wallets. They have checklists of important points they look at and try to be as thorough and impartial as they possibly can.
As you say, there are now hundreds of wallets, each of which update at least every few months. So as you can imagine it's a lot of work no one is getting paid for. It's also pretty ungrateful work as accusations of unfair treatment of a specific wallet is easily made, while at the same time if they list a wallet that turns out to be even more insecure than they reviewed it, or turns out to be malware and people lose money, then people will also be quick to blame them.
Blockchain.info for example has been notorious for bugs in their wallets that have cost loss of bitcoins in some occasions. They were delisted at some point, leading to a lot of controversy and accusations on the forums. I don't know if they are currently back.
Personally I'm happy they err on the safe side, even though that can be a big nuisance for wallet developers.
I would assume the short answer to your question is that the work simply hasn't been done yet: not all (latest versions) of all wallets have been tested.
As always in open source: you're free to volunteer to help do the work.

user21052: I asked Craig Watkins, Bitcoin.org's wallet page maintainer, to comment.  The rest of this answer is his reply.

Currently on bitcoin.org there are 21 wallets listed (including three
  "hardware wallets").
Bitcoin.org is a community maintained site:
  https://bitcoin.org/en/about-us
Updates to the wallet listings are submitted as pull requests on
  github: https://github.com/bitcoin-dot-org/bitcoin.org
and approval for listing is based on community consensus of complying
  with the criteria listed here:
  https://github.com/bitcoin-dot-org/bitcoin.org#wallets
The pull requests can be submitted by anyone, but are most often
  submitted by the wallet developers themselves.  Reviews can be
  performed by anyone, but are usually done by the current bitcoin.org
  wallet maintainer who offers an opinion on the compliance to each
  criteria listed.  The reviews, discussions, and results for each of
  the current and past pull requests can be viewed here
  https://github.com/bitcoin-dot-org/bitcoin.org/pulls


35795: <p>At this point there are hundreds of Bitcoin wallets available <a href="https://bitcoin.org/en/choose-your-wallet" rel="nofollow">https://bitcoin.org/en/choose-your-wallet</a></p>

<p>Clicking on a wallet reveals some areas where wallets are compared: </p>

<ul>
<li>Control</li>
<li>Validation</li>
<li>Transparency</li>
<li>Secure Environment</li>
<li>Privacy</li>
</ul>

<p>Some excluded wallets are superior in some of these categories than the wallets listed. Is there a formal review process or criteria for wallet inclusion that someone can reference for me?</p>
 5292: <p>I don't know all the details, so if anyone has a better answer, please post it.</p>

<p>There are several volunteers that spend a lot of time reviewing and comparing wallets. They have checklists of important points they look at and try to be as thorough and impartial as they possibly can.</p>

<p>As you say, there are now hundreds of wallets, each of which update at least every few months. So as you can imagine it's a lot of work no one is getting paid for. It's also pretty ungrateful work as accusations of unfair treatment of a specific wallet is easily made, while at the same time if they list a wallet that turns out to be even more insecure than they reviewed it, or turns out to be malware and people lose money, then people will also be quick to blame them.</p>

<p>Blockchain.info for example has been notorious for bugs in their wallets that have cost loss of bitcoins in some occasions. They were delisted at some point, leading to a lot of controversy and accusations on the forums. I don't know if they are currently back.</p>

<p>Personally I'm happy they err on the safe side, even though that can be a big nuisance for wallet developers.</p>

<p>I would assume the short answer to your question is that the work simply hasn't been done yet: not all (latest versions) of all wallets have been tested.</p>

<p>As always in open source: you're free to volunteer to help do the work.</p>
 21052: <p>I asked Craig Watkins, Bitcoin.org's wallet page maintainer, to comment.  The rest of this answer is his reply.</p>

<blockquote>
  <p>Currently on bitcoin.org there are 21 wallets listed (including three
  "hardware wallets").</p>
  
  <p>Bitcoin.org is a community maintained site:
  <a href="https://bitcoin.org/en/about-us" rel="nofollow">https://bitcoin.org/en/about-us</a></p>
  
  <p>Updates to the wallet listings are submitted as pull requests on
  github: <a href="https://github.com/bitcoin-dot-org/bitcoin.org" rel="nofollow">https://github.com/bitcoin-dot-org/bitcoin.org</a></p>
  
  <p>and approval for listing is based on community consensus of complying
  with the criteria listed here:
  <a href="https://github.com/bitcoin-dot-org/bitcoin.org#wallets" rel="nofollow">https://github.com/bitcoin-dot-org/bitcoin.org#wallets</a></p>
  
  <p>The pull requests can be submitted by anyone, but are most often
  submitted by the wallet developers themselves.  Reviews can be
  performed by anyone, but are usually done by the current bitcoin.org
  wallet maintainer who offers an opinion on the compliance to each
  criteria listed.  The reviews, discussions, and results for each of
  the current and past pull requests can be viewed here
  <a href="https://github.com/bitcoin-dot-org/bitcoin.org/pulls" rel="nofollow">https://github.com/bitcoin-dot-org/bitcoin.org/pulls</a></p>
</blockquote>
