The way I think of it is that clicking on the title is taking you to the content. For a self-post, the content is posted on reddit itself, so the content location is the same as the comments page.

That being said, they've made a few steps toward something closer to your suggestion in some places. For example, if you do a search, the search results behave this way, where clicking the title always takes you to the comments and there's a separate link (with a chain-link icon) to go to the linked content.