Does anyone else agree or is it just me?

Some people simply don't care enough to reciprocate. This is valuable information and should be regarded as such.

I often tell people you find out who your friends are when you move. Being one of the few males in my social circle with a good back, I get asked to help people move a lot. I am shocked how few people will help a friend move, even if that friend helps them all the time. One woman I know had 3 of her lovers back out of helping her move but some of her coworkers showed up and pitched in.

Otoh, be careful about offering unwanted help. If someone doesn't ask for help, volunteering and inflicting help on them can be seen as patronizing and arrogant (get the feeling I have encountered this before?). In such cases, returning the favor is unlikely.

I agree fully with AJtogo. The fact is that you have to get around the whole idea of keeping score. The thing is that if you do favors for people they will generally pay you back at some point down the road. Also, keeping score hinders you socially, these people can sense through your non-verbal actions that you are disappointed in them and will be less likely to help you out.

Also, like AJtogo said, it's tacky. I actually am the opposite. I don't like people who keep score.

Happy are those who do not expect thanks, for they shall not be disappointed.

It's great when favors are returned but an expectation of a returned favor is tacky. Favors are done out of friendship and kindness, not for gathering obligation.

Personally I get annoyed if people help me out just because they feel obligated. I help people (or not) because I want to (or don't) and not to get them to reciprocate. I expect the same of my friends. If you have a good relationship with someone, be it friendship, dating, family, whatever, you should care about them enough to WANT to help them regardless of thanks or whether or not they help you out in return. Of course, if you're so close then ideally they would feel the same and naturally assist you in your "time of need" as well. Not because you helped them once, but because they want to because they care. If you find yourself constantly giving and never receiving then you have to consider WHY.

Maybe, as the other answerers have suggested, people sense that you are helping for the wrong reasons or that you have certain unreasonable expectations, or that you are not grateful or are "keeping score". If that's the case, then that would be why they fail to ever come to your aid. Another possibility is that you are choosing to have relationships with the wrong people. You're picking friends and dates and whatnot for some other reason than whether they are truly good for you and care about you. You're young so you could easily be at that age where you are choosing people to hang with based on who has the right image, who is cool, and various other nonsense reasons like that, which mean absolutely NOTHING once you get into "the real world". In that case, your problem is your choice of friends and you need to find yourself some new ones that will actually like you and care about you for who you are and not any stupid superficial (not to mention immature) high school reasons. Another possibility is that you aren't that close to these people at all. In which case you are expecting way too much of people. You can't expect strangers (or mere acquaintances) to go out of their way to help you just because you once helped them. Expect your family and friends to be there for you, but not people you hardly know.

And before you get upset and start having a tantrum like you did with some of the other answerers:
1) It's hard to answer your question when you are so vague about it. You're getting frustrated that people are making it harder than it needs to be. Well we're not mind readers. Your question is vague which leads to interpretation. You're more likely to be misunderstood that way and less like to get the answers you seek.
2) The people on this site, myself included, without knowing you AT ALL have tried to offer you some help by answering your question. Rather than appreciate the effort, you pout and yell because you don't like the answer?! Maybe THIS is why nobody wants to help you?

I help people because I enjoy doing so, not because I want them to feel obligated to return the favour. It's nice if they do, but it's not like a requirement or anything.

I help people because I like doing it, not because I expect anything in return. If you expect an immediate return on your favor (or if you expect them to repay you in general), you're not doing it for the right reasons.

I'm not sure if you just mean on this site, but either way, that's not how it works. In real life, you'll end up helping the people around you so many times, and they'll do the same for you, so you can't even keep track of who owes who. And on this site, there are no obligations--you're just supposed to answer other people's questions and ask your own.