They warm up things that a) I don't want to put in a kettle and b) don't want to put in a dedicated pot to put on the stove.

Like the remainder of the soup i made yesterday that I've put in a china bowl in the fridge. I was able to eat warm soup out of that bowl without requiring to make any other dishes dirty. Pretty convenient if you ask me.

Bonus: you can take a cherry tomato or a single grape and make a small plasma arc in the microwave. Pretty cool trick to impress and scare people at house parties.

They also heat other things up like food but take less space than an oven.

I think you might have a terrible plate problem instead of a terrible microwave problem

I'd like to see you make popcorn or an omelette in a kettle. Or heat up rice / soup / stew