Boyd,
We're in a low flying aircraft and outside range of ATC and have an emergency of some sort. As pilot I will do my broadcast on the appropriate ATC freq and which all the other aircraft in that area are listening to. Whereas you will do your broadcast on 121.5 which some aircraft may or may not be monitoring.
Pray tell, who do you think has got the better chance of being heard - you or me?
I've got nothing against monitoring 121.5, what have you got against ATC frequencies being shown on charts?