unspoken rules

we've worked at home a lot over the past two and a half years. it's been both good and bad. we're mostly back in the office these days, but i do still work some days at home when i really have to concentrate. or because my back is hurting, which it has been lately. i'm having flashbacks to the back surgery in 2015 and hoping to avoid it happening again. though working at home probably contributes to it, as i tend to sit much more when i'm home - forgetting to take breaks or eat lunch. 

but it can also be weird being back in the office. a whole new set of rules came about while we worked at home. and many are unspoken and just understood. or not understood. and it's weird, since they're unspoken, to feel disappointed or annoyed when the rules are broken, but the fact remains that i find myself feeling disappointed and annoyed of late.

a couple of examples: 

1) calling on teams: when you call someone on teams, you send a message first to ask them if they have time. so it's super annoying and jarring when when someone just calls out of the blue. often when you're in the middle of a meeting, so they don't even pay attention to the little red bubble that shows that you're busy. 

2) meetings in an open office environment: during corona, we all sat at home and could therefore hold meetings out loud and not bother anyone but the cat. back in the office, it's an open environment and there are some phone booths for meetings where you're the only one, or there are plenty of meeting rooms if you're several people meeting with others on teams. however, i've noticed that some of my colleagues continue to hold their teams meetings in the open environment. they put on headphones and don't realize that they're shouting. one colleague actually had a meeting on teams with the person sitting directly across from him. hello? go to a meeting room, or just go around to the other side and talk to one another! by the end of the day, i was utterly exhausted from listening to his shouting during all his meetings and i was too mad to say anything about it. but seriously, has two years of working from home rendered him so unaware of other humans that he doesn't realize he's being utterly rude to his colleagues?

how is company culture formed? who decides the etiquette? and how does everyone agree on it without talking about it out loud? and when someone utterly violates it, how do you talk to that person about it nicely? i know for sure that you don't let yourself steam about it all day and get so angry that you know you won't be able to be nice about it. but then the moment passes and maybe now his way of just holding meetings with headphones and shouting has moved everyone towards establishing a different company culture than the one you thought was there. and it's all unspoken. and it makes being back in the office less fun than it should be, because it truly is nice to be around your colleagues again.

but i still think a combination will be best. i need a couple of days of being able to concentrate at home and a few days of being with my colleagues in the office. they're two completely different ways of working. and i like the variety, but i do just wish we all agreed on the culture.