Masturbating while I’m there?

My bf and I live together and I notice sometimes when I’m in the room next to him (fully awake and capable of pleasure) he masturbates in the bathroom. I have no problem with this when I’m gone or asleep etc. but when I’m there it’s jus a bit rude? Especially when he’s probably fantasizing about someone that’s not me? If you have a snarky comment please keep it to yourself. I was in an abusive relationship before so these things genuinely bother me. I talked to him about it but I think he still does it. Does anyone know why? Do men need to do it several times a day or something?

Thank you.