Certainly I try to phrase what I want from my son in terms he can follow, and I try to give reasons.

"Please sit quietly on this bus because it's not safe to stand up while it's moving, and there are lots of other people that don't want to hear you making a loud noise."

(We are still working on that; also on the horrific idea that other people may want to sit in his favourite seat.)

But honestly, if one of my parents said to me "I expect you to be on your best behaviour" I would take that as an instruction at face value without the guilt-inducing subtext you have added. In a more destructive parent/child relationship I can see that subtext existing, but the word 'expect' doesn't have to imply it.