the people i've met and threw away - or being thrown away

I've been recently thinking that we actually consume the people we've met. I am talking about the people, who you've talked just a couple of times, met totally randomly and after some time you forget that they even exist. There are tons of such people, who I wanted to somehow keep in touch with, because I really liked them. But after this thing is over (some occasion, doesn't matter), I never saw them or contacted them. I feel like I'm using (or being used like) a disposable battery and throwing it away (or thrown away). I have absolutely no idea if people are feeling the same way and there is nothing I can do. I don't want to be some sticky person who doesn't let go and makes a big deal about every friend she makes. That would repel the others, wouldn't it? Well, I think it would and that's why I can do nothing about it. I've been trying to contact these people, making effort to be nice and friendly within the borders of casualness (maybe sometimes not even though I try), without seeming like crazy or needy or desperate, but they just don't care. I also thought that the reason why people don't want to (I don't think that they specifically don't want to see me again, they just don't give a damn) or at least don't try to keep in touch is maybe my attitude in the first place causing people to stay away. I also gave this thought a try and just didn't do anything, acted cool and wanted to see what will happen. Well the result is not very surprising: nothing happened. So, I came to a conclusion that people just don't care. Or I am not likable. Either way, this makes me kind of sad.