The feedback was more than just "Please be on time". It was proceeded by multiple statements on the impact of being late. The fact that you should be on time is obvious, but the impact of not being on time isn't always obvious.

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.