I know it's heresy to the British, but you can heat water for tea in the microwave just fine. And at least in my European imagination, every American has a microwave in their home.
I don't heat up leftovers, I just eat them cold. But we do have a microwave (we bought it at the beginning of the pandemic so we could heat up frozen meals--we didn't have one before). I had cold leftover pasta for lunch today. My wife turns up her nose at cold leftovers but I'm not picky.
You can end up superheating the water that way and scalding yourself. I also prefer to control the temperature of my water which you cannot do in a microwave.
It's something to be aware of, but in practice it's very difficult to superheat water at home.
For superheating to occur, you need very pure water in a smooth container with no imperfections. Tap water in most places cannot be superheated because it contains too many minerals, and most ceramic cups aren't smooth enough to prevent boiling.
If you're making tea, an easy way to prevent superheating is to drop the bag in the water before you heat it. Another way is to put a wooden stirrer in the cup.
There's a mythbuster video here where they show water being superheated: https://www.youtube.com/watch?v=1_OXM4mr_i0, but note that they use distilled water (which nobody drinks) in a Pyrex container (which nobody uses). And they actually use a mug of tap water as a control.
that's not really true. i've superheated tap water at least a dozen times. never had a negative consequence from it, besides having to clean up some water, so it's also not something that really bothers me. from my experience the superheated state can be surprisingly stable, a couple times only explosively boiling over while being poured, instead of the moment I grab the container.
edit: as far as 'nobody' using Pyrex, my preferred container for heating water is a big Pyrex measuring cup.
> It's something to be aware of, but in practice it's very difficult to superheat water at home.
Eh, I've had it happen many times at home. A coffee mug of water comes out of the microwave with just a hint of bubbles. Add sugar/tea/instant coffee and the whole thing instantly bubbles up and spills.
My microwave has a picture of a cup with a spoon in it to warn you to only boil water with something in it. Despite being warned for years not to put anything metal in a microwave it's actually fine to leave a metal spoon in water to stop it from superheating.
You can burn yourself with an oven or a hob. In fact a kitchen is full of ways to maim yourself. So why single out the microwave? A microwave is a tool, tools can be unsafe if used improperly.