Microwaves are pretty terrible, and proof that wide consumer adoption does not really indicate quality or suggest that consumers adopt technology which _should_ exist.
I lived without a microwave for a ~year and ended up buying one again because they are pretty convenient.
So maybe it's not high on the list based on the value you are measuring but it definitely has a convenience value that isn't replaced by anything else.
The generations of microwave after the first few were fantastic. They did what they were supposed to and lasted decades. Once that reputation was solidified, manufacturers began cutting corners, leaving us with the junk of today.
The same thing happened with web search and social media. Now, those selfsame companies are trying to get us to adopt AI. Even if it somehow manages to fulfill its promise, it will only be for a time. Cost-cutting will degrade the service.
I grew up in a country where microwaves were not a thing. When they suddenly got introduced, it felt like a miracle even just for the ability to quickly heat things up.
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 are not. But they are the AI slop of cooking - it's easy to get an acceptable result, so people associate it with junk food made with zero effort.