I don't think typical hobbyist is interested in mains voltage at all.
Almost every beginner who gets a scope wants to "look at the mains waveform" as the first thing out of the box. Don't ask me why. I assume when they get a meter that's the first thing they do, they jam the leads into the wall.
I think you're right. It's an immediate source of a sine wave (more or less) and the value should be pretty well known.
Threads start up here all the time about testing mains with some piece of new test equipment.
I maintain that using a DMM on mains is a waste of digits. A solenoid style tester is my favorite because I just need to know the order of magnitude of the voltage (120,{208-240-277},480) and, since there isn't anything I can do about the 3rd decimal place of line voltage, there really isn't much point in measuring it. The voltage is either present and in one of those 3 bins or it isn't.
You can tell the voltage level with a solenoid style tester by how hard it jumps in your hand and how much it vibrates. Also by the arc when you remove a probe. This is close enough! With this style tester, I don't have to take my eyes off the probes (and what I'm probing) just to hang by my knees trying to read the DMM.
Maybe I spent too much time working on industrial automation. Way back when... Side issue: My issued Simpson 260 circa 1969 didn't even have a CAT rating, yet I'm still here!
https://www.amazon.com/Knopp-K-60-Cat-Number-14460/dp/B003A7T5KG