Unfortunately I am serious.
Its not just CAS busts that folk turn them off.
And to be honest I don't think its your average PPL that does turn them off. Its the ones that do know the rules and do know how the system works that are turning them off for "tactical reasons". Ie the ones that really don't care if you MOR them because they know the rules and know they are legal.
No evidence for
Rule 5 busts
Noise abatement busts
Danger area busts (where the calibration of the radar has been know to be out for several years ie your 3 miles off shore feet wet and they reckon your flying over the land)
etc etc.
By far the most common tactical squawk reason for controllers was so certain Mil units couldn't see them. Along the lines of if those bastards can't keep there traffic away from my approaches and co-ordinate when I am doing radar they can go
themselves if they think I am going to help them. There are other issues with being seen by Mil units but personaly I prefer to have the squawk on and refuse there suggestions than not having TCAS aircraft not be able to use my data.
Another issue is that some airports want the mode C in a circuit and others don't. I had one visiting pilot get his ear chewed out on frequency for having it on. When he informed the controller he was just obeying the current AIC on the subject he got an ear full.
So there are many reasons why people don't squawk.
PS please note when I have one and it is working I always have it turned on to Charlie.