Right, but if you find it obvious that one should be on time, yet you aren't, there are two possible explanations:
- You are trying to be on time and failing, in which case telling you to try harder is unlikely to help. There is an underlying cause for your involuntary tardiness that must be addressed; or
- You are intentionally disregarding being on time, because something has made you think that is acceptable. There is an underlying cause to your voluntary tardiness that must be addressed.
Either way, people generally have a reason for doing things the way they do them, and willingly ignoring this reason is generally ineffective at provoking change.
Everyone responds to feedback differently. I'm personally a very direct person, and asking whats preventing me from being on time is just going to make me feel like you're talking down to me. Understanding why it's important is enough, let me be a big boy and figure out my own time management. Others hate being told what to do, and would prefer to work through a solution collaboratively.