Nice vs. Real

I've noticed a lot of the time when someone asks for advice and someone gives them "the real" ppl tend to say if you can't say something nice don't say nothing at all. Now I can't speak for everyone but one thing I know is if I ask for advice I expect to get the "good, bad, and the ugly". Don't sugar coat it for my feelings just give me the "real". I mean what's the purpose of advice if everyone is just gonna be nice about the answer?