So does plastic.

Also, it's a microwave oven. Who thinks that you can stick your hands on something in a device called an "oven" and not get burned?

Plastic with a brim is going to be cool, where glass with a brim will be hot.

The reason why glass vessels become hotter in a microwave oven is because glass has a much higher thermal conductivity than plastic, so it becomes heated from the hot food.

Using two pieces of cloth (e.g. cut from a small towel) to hold the hot glass vessel is enough to take it safely out of the oven and this negligible inconvenience matters much less than the undesirable effects of heating food in a plastic vessel.

I put my bare hands inside a microwave and pick up the paper or plastic from inside all the time!

The entire point of using a microwave is convenience. If I'm going to have to break out the oven mitts, I may as well just use the oven or an air fryer.