Flying around Europe I've lost count of the number of times I've had to stop monitoring 121.5 because of all the "noise" going on there. And it's not the "practice PANs" that bother me, it's mostly the "meeow"s and "Franco"s or someone lost between frequency changes who needs like 20 different back and forth interactions to get onto their correct frequency.
I just keep it in the background but at a much lower volume than COM1.