It’s a good question. And your initial point is correct - prior to God changing the wafers, they are just wafers. The security is for the post-changed Hosts; because they are distributed to (what we hope are) the faithful. At this point, someone can pose as a Catholic and walk off with the Body of Christ and carry on with whatever evil intent they have planned. That’s what security is trying to prevent.
I think there are benefits if receiving on the tongue was the norm, but I doubt it would help to stop this. I mean, if you are intent on doing this and to be able to keep doing it without being caught, why try to be Gaylord Perry at the head of a line in front of everyone? Just go back to your pew and take the Host out of your mouth there, no matter how it got there. Why would satanists care if it was somewhat physically degraded?
Freegards