Dunno where you're from, but where I'm from, it is pretty much the opposite world. You're a red flag if you don't see yourself as having fun. Yes, this includes most webdev shoves where one does the equivalent of shoveling virtual manure. (No, I don't agree with this, either).

>Why do people think they can "play with new technologies" at work

Because software dev is a step above code monkeying and people value being able to grow. Which requires experimentation.

It's unprofessional when there are higher priorities or you can't make a potential business case.