There are large advantages to shelling out though.

1. Not reinventing the wheel

2. Implicit use of multiple cores

Things could be improved I agree.

For example posix_spawn() could be efficiently implemented on glibc to avoid kernel overhead for fork()+exec() from large processes. Then language runtimes could use that to implement their "shell out" routines.

Also pipefail doesn't cater for SIGPIPE as detailed at http://www.pixelbeat.org/programming/sigpipe_handling.html which can be awkward.