--everyone
And, worse case scenario, you spend like 5 minutes occasionally doing it and now have access to a clean microwave, without needing to buy more e-waste and encouraging the production of cheap, stupid things like a water bottle with a heater in it.
Alternatively, if you mention you cleaned it, they'd be more inclined to say that you're the one who cleans it.
You pass responsibility to someone who isn't responsible. You don't recognize this function repeats and people become over burdened. Sure "It's not a big deal" but that's in isolation. That's one time, one task. These things don't just add up, they compound