Originally Posted by antarius

They do it to show you how it feels, so you don't mess up your use of force procedures just because you think "it's only pepper spray" (its in a Use of Force 8 hour block [class] )

The idea is, if you know how crappy this stuff is; you wont use it unless you have to, on a civilian or another officer if it ever came to that. (Cant imagine it would)