Stack Exchange was built on a central philosophy of making information super easy to find. In a world of forums, it can be extremely difficult to actually find what's being asked, and worse, what the answer is.
Because of that, we try to avoid "polluting" the question-answer stream with tons of comments like "this really helped me!" or "thanks!"
That lack of comments should never be confused with thinking you aren't helping people. Chances are, you are.
People solve real-world problems every day here on the Stack Exchange network, and the way appreciation is shown is through up-votes (and to an arguably lesser degree, accepting answers). When a user sees a post that really helps them, they'll often up-vote it. That, as I'm sure you know, gives the poster some reputation points (five for a question, ten for an answer) to say "you did really well with this."
It can be hard to quantify these sorts of responses when reading through posts, simply because comments can be a lot more obvious. In other words, we'll likely pay a lot more attention to five comments than five up-votes, just because they take up for space on the page and give us more to read. Since comments like "thanks!" and "+1" are discouraged, many comments can, after a while, begin to look critical.
But that shouldn't be taken to mean that people aren't appreciative. Even those critical folks (commenters and voters alike) are just trying to keep the site as close to ideal as they can, so that it can--you guessed it--help that many more people.
I've taken something of a detour from your actual question, the answer to which is along the same lines. The best way to show appreciation is through votes, so you don't see a lot of blog or meta posts here that say "this really helped me!" just because they don't really teach anyone anything. There are definitely a few out there, and I know Infinite Recursion was nice enough to link to one in a comment above, but I hope you don't take the relatively small quantity of such posts to heart, or to mean that people don't get real-world help.
There were 21 million up-votes in 2014, which roughly corresponds to 21 million times someone found a post helpful or useful. That's not too bad.