ubiq: Yes. If a kid is in a MO school where *no one* wears a hat, and he wants to, he often will not wear out out of such pressure.
What if the kid wants to wear yellow or blue or grey pants? Should anyone dare stop him from choosing his dressing preferences?
When someone who grew up wearing a black hat and black yarmulka and then changes by dropping them, he is making a statement against his frum community.
When in the military you can’t be creative in clothing. You wear what you are told to and given. The same uniform as every other soldier. Same for Hashem’s people. You identify with Hashem’s children.
Bottom line: When a Jew walks in public, weekday or Shabbos, he should be wearing a hat.