Cleaning is a routine maintenance job, whether they’re rim or disc brakes.
Of course, not all bikes get routine maintenance... I started tinkering with my hybrid hack yesterday, which hasn’t had any actual maintenance for gawd knows how long. I’d intended to spend 20 minutes max on it, but ended up getting lost in three solid hours of fettling, including restoring the brake pads (turns out they aren’t black after all, they’re orange).