I mean, I get it. It's a silent night. Babies and livestock need not to be woken. I get it.
But. "Silent Night" has a really enormous range, and some of those notes are high, and you have no chance of hitting them if you don't support them. Which is hard to do quietly unless you're actually a good singer, which most people in your bog-standard group of carollers are emphatically not.
So what you end up with is some nervous keening and cracked notes. Which I'm sure the Christ-child forgives, but he shouldn't.