i started in LE in '64. That was an era of a variety of such devices. Especially since it was before MACE, although Kel Lites came into use in the late '60s.
Since we were a Sheriff's Department, we were solo and isolated a lot.
I carried a flat slapper. Still have it, on a trophy shelf now.
IIRC I only used the slapper around half a dozen times. I preferred to talk down suspects if at all possible. I think I was pretty good at it.
But there were times when either the conversation dried up, or I never had the opportunity to start it. But when I did use the slapper, it really took care of business.
When it was over and my arrestee had no further interest in further combat I would counsel him that I would pass on his lack of cooperation to my fellow troops, so that if he tried this again he would meet at least the same fate. Oh, and tell your buds and relatives too.
Sometimes that is the only way education can work.
Over time as MACE and aluminum flashlights became so commonly carried anyway interest in slappers, saps, etc waned. As useful as mine was, I did not miss it.
But without a doubt it made me safer.