Why shouldn't an unsolicited email asking for opinion include the links to the articles? I have a precursory research – that is, an article posted in my website to know what I want to pursue – and want to send to a professor to have his opinion. However, I was advised to ask him if he has time to read my ideas first before sending links to long blog posts. 

I wonder why that is a case. I understand that this is to show that I respect his time – a professor has many duties – but I think in the end it depends on the interestingness of the content. If it is interesting enough, then no matter how long it is, it is still, well, interesting. And I think this factor is basically the relevance of my email to his work. As explained in this answer, as long as the email is relevant it can be answered. 

In my case, it has raised some interests to others in tangient fields, and matches one of his research interests, so I don't think there should be a problem. What may be a problem is that he may be reluctant to click on an unsolicited link, or the articles are long. But I suppose this is a normal thing that researchers do all the time? All of the problems here – sending unsolicited email to ask for opinion, putting the article in a link or attachment to keep the email short, putting the ideas in blog when they are just initial observations – don't seem to be problem to me. 

Think of the email like this very question: I ask you unsolicitously, you may have a lot of duties, and there are three links on it. If I don't need to worry whether I am wasting your time reading this question, then why should I worry I'm wasting his time?  The email is much shorter than this question. I don't see why there should be extra cautious.

So why does the person advise this? The full draft of the email can be read here.



Minor question: Should I put tracking links?
I don't think the issue is specifically the links, but that you seem to be asking a lot of the recipient in the initial mail, with, perhaps, too much information. The professor isn't likely to want to follow up on that before contacting you. 

On the other hand, not making the information available at all would be an opposite mistake, requiring an additional email just to get access. 

The first part of your mail is fine (taking students? interested in xyzzy). But then you could just put nearly all of the rest of it on the web site and provide a single link:

"My current interests are explained at ... Sincerely..."

So, more than nothing, but less than what you have would be, IMO, a better balance.