Because we can! That's why!
Corwin-Arms sells them.
https://www.corwin-arms.com/product/vz-58cz-858tavor-kal-tec-16-ar-15-style-bayonet-adaptor
I actually have one kicking around here somewhere. I was going to mount it to my 10/22, because as anyone in Miramachi will tell you, the 10/22 is an evil assault weapon in need of tight regulation.
It works with STANAG compatible bayonets (M16/AR15 style bayonets).
Because we can! That's why!
Did the ring on your M7 bayonet fit into the groove on you flash hider?
Mine is too wide for the grooves in my Norico birdcage.
The Flash hider grooves aren't for bayonets, but other accessories that clamp directly to the flash hider. Bayonets are meant to just hang off the barrel