As you might imagine, overwriting vtables in memory is a common technique to hijack control flow and making your program execute attacker's code in an exploit.
Patching function pointers in general is very desirable thing to be able to do when writing these kinds of things. vtables are interesting because unlike normal C function pointers they can only be used in a standards-compliant manner in a few very limited ways, so if you’re implementing control flow verification you can really ratchet up the security for these. For normal C function pointers, sadly, the best you can do is usually very little, if anything at all. Especially because the use of non-compliant constructs like forging ordinary function pointers is extremely common in things like language runtimes.
