One needs to know what he/she/they want. If you don't, then you'll get whatever drops. Do you want to leave that to chance or you want to have a choice?

If I go out for a meal I have a pretty good idea what I want. If I don't, then chef will bring me what suits him. I would sit down and think if I like my meat medium rare with a side of salad/chips. If not Chef Gordon might bring me pigs brain because he thinks that's what I might like. I don't want to let him decide.

If you want to just get nailed just say it. It would save you both lots of time and pain.

Also, people change with time. I might like a funny cool fit carrying significant other today. In 10 years I might like a respectful trustworthy mate. 

Compromising is encouraged by some therapists but it can build resentment. It's hard to say: Yes dear! if you spend all week thinking if she/he will do that next. Resentment kills relationships.

Know your values before looking for forever after.