I noticed this about a year into doing audio, my headphones mostly stay in my bag nowadays unless I'm using them to check a live stream/ record mix or to line check something. My mixes have 100% improved when i actually started focusing on the room sound and not what the headphones sounded like
I never attempt to mix FOH via headphones, because that's obviously not what anyone else is hearing, but aside from checking sources I use them quite frequently in smaller venues to check what's stage volume and what's via the PA. You can better understand what changes to make when you know which components/proportions of the mix are actually going to be influenced by that. Things are what they are and they do what they do. It's really just about making solid decisions on the basis of that rather than rote learned rules of never do X, always do Y.
Bro. With the mains at reference level, the low end will still creep into your ears and will combine with the low end in your headphones or IEM. PFL is for finding and correcting source issues.
Sound booths at certain venues (mostly lecture halls, laddered conference rooms and banquet halls) are set ike a piece of sh** beyond common sense (located behind or at side of the stage, have no openable windows but fixed glass panes like a prison cell etc) so that the direct PA sound is impossible to be heard properly, making the use of headphones inevitable in these cases... WIth headphones on the mix might sound strange, but without headphones all I can't mix at all :-(
There are always exceptions to the rule. Know what your options are and being mindful of the situation. That’s what separates the pros from the rookies most of the time. Thanks for watching!
