Common courtesy
“It’s occupied!” is a common phrase to yell when someone (usually a boomer) knocks on a clearly locked bathroom door. While we must give boomers points for enacting common courtesy, it’s probably even better to assess whether the bathroom door is locked or not.
Most likely, when the door is shut and the light is on, that means it’s occupied. This habit may irritate millennials, but in the grand scheme of things it’s not a big deal. I mean, some of the other grievances on the list are a lot worse than this one. Yes, no one likes to be disturbed while doing their business, but it can be worse.