No, they actually don't. It constantly gets drummed into young teachers in England that "the little things matter", "insist they stick to the small rules so you won't have to worry about the bigger issues"...That's just bullshit.
I never wore school uniform. My teachers didn't care what we wore. It had zero impact on our learning or our grades. I didn't have to walk through corridors in silence, we could sit where we wanted in class, we brought our own equipment and borrowed stuff from classmates if we forgot. Surprise.. no unruly behaviour in class. We were allowed to go to the toilet when needed. No stupid comments or threats. After all, we were responsible for our own learning. I didn't know anyone, who ever got a detention at my school. It just wasn't done. (I assume our teachers had better things to do than spend more time in a room with kids, who had annoyed them...) The teacher is there to teach. It's a bit like the horse and the water...
And no, I didn't go to some fancy private school. I attended a bog standard comp, albeit abroad.
It's like parenting. Pick your battles. Is whether a kid goes to the toilet in a lesson really an issue? It's only an issue if you make it one. They either need to go and then they are back after a few minutes,...or they use it to get out of the lesson. Then it would be more useful to find out why that's the case and how you can support them in not having to hide in a stinky loo.
The undone top button doesn't distract from the lesson. The teacher making an issue out of an undone top button or a wonky tie or an untucked shirt causes a distraction.
It doesn't stop a child from accessing a lesson when they don't have a pen and quickly ask a friend to borrow one. It stops them if the teacher makes an issue out of it, refuses to lend out equipment and spends ages just going on about it.
I have found children to be much more relaxed and increasingly more reliable about these things when the teacher doesn't "sweat the small stuff". There's no fun in sneaking to the loo when it's perfectly fine to do so. They're much quicker organising a pen and more reliable in returning it if it's just normal that equipment is available. (It's my stuff...they don't tend to throw or break my stuff,...because they do generally quite like me and I tend to have a positive relationship with my classes and my students' parents. I'm apparently, "really strict but funny'.)
I used to work in an office before becoming a teacher. People would wander off for fag breaks whenever they fancied, they'd wear what they wanted, have little chats in the corridor, go the toilet when they needed. I didn't need to bring my own pens. We had pens and nobody tried to make me stay longer for using one.