Zs can grab you, and you can grab vehicles. So why cant we grabs dogs or wolves or w.e. and stop them from fleeing/make them take penalties?
Because no one implemented it yet.
There is one (tolerable) issue with grabbing critters and possibly NPCs: we don’t have a good way of identifying who is grabbing and what is being grabbed. There are some hacks around it, but it makes it harder to write grabbing.
Plus, critters (and possibly NPCs) should understand being grabbed and start fighting back rather than just fleeing.