Ken Thompson wrote a regex engine which compiled (at runtime) regexes into data structures containing executable machine code, and invoked them (from C source) by jumping into the data i.e. treating its location as a function pointer. That's what's happening here except it's the start code inserted by the linker which is jumping into main.

So there's the utility, if you're hardcore enough to build machine code at runtime.

If you wanted to abuse main() particularly, I guess you've got argc and argv in registers, and your hand-compiled main 'function' could maybe have some self-modifying code?