Only nice to get something?

Why are people only nice when they want something from you? I hate and yes I mean hate when people who don't normally be nice to me try to be nice so they can turn around and ask for something. If you can't be nice all the time then don't ask for nothing. Cause it don't work on me. Be real and not fake. You never know when you will need something from someone so why think that you can do what ever you want and get what you want. Treat people the way you want to be treated.