PeachCream, you just sound like a really nice person and if other people don't just appreciate you for who you are and your intentions at the time then that's going to be more down to them than you. That's their misinterpretation of the situation not you.
I'd say that it would be a really sad world if people don't show someone that they are interested, they care, they want to help them or be there for them just because they're the "wrong" gender. I think that it's good that you care/want to help.
I mean you may be right, that there may develop an attraction there sometimes with the opposite sex (or your own sex- not everyone's straight!! ), but that can be as much because you're just so "nice" and understanding. You shouldn't have to change the way you are though, and you are going to be making a real difference to some people, regardless of gender, without the attraction bit, and that really matters!!
Just try not to be doing that just as a route to building friendships though, if you are, or at least see that things become more "equal" as the friendship develops. They should be there for you/giving something back as well remember.
And keep in mind other ways of making friendships too e.g. just talking casually to people inc. about yourself, finding things to do with them which you both enjoy, finding similar interests, sharing thoughts/opinions, finding things you have in common or differences you like about each other...................
Although, if it helps with the "right now" then maybe you could just be a little (more?) attentive to any signs/what people say/do that they want to take things further/to relationship level. Then if you're not interested then simply put them straight at the time.
Alison