Yeah, but forking to exec immediately afterwards is the common case. If
you make that some weird nonportable new variant, 90% of programs are
never going to use it, and none of the rest will until some considerable
time has passed (time for this call to percolate down into the kernel and
glibc --- and try getting this call past Ulrich, ho ho.)
(Anyway, we *have* fork_to_exec_soon(). It's called vfork().)