It's also possible that Fett kept his helmet on to hide that he was a clone, as he told Din Djarin that the Empire would likely recognize his face. Thanks to The Book of Boba Fett, it's clear that ...

Boba Fett's reputation as a cool and enigmatic character ... His elusiveness and lack of dialogue, as well as the fact that his face is constantly obscured by a helmet, made him instantly ...

You would have people walk by and go, ‘Oh, there goes that crappy kid that played Boba Fett.’ And I’m like [makes confused childlike face]. And they’re like, ‘Oh dude, he sucked.