I've noticed that basically no system I've ever worked with has /bin/sh as a real executable. It's always a symlink to dash, bash in POSIX mode, or something similar.Why? What are the disadvantages of using the true, original /bin/sh? (Speed? Licensing?)
Why does no one use the true Bourne shell as /bin/sh?
shell;history;dash
I'd guess lack of features - no command history, no fancy redirection, no command line editing. BSD introduced csh the C shell for those reasons.  Another factor is that the Genuine Bourne Shell was only recently available in open source form. Unless you licensed it, you couldn't distribute it.  That put it out of reach for free-of-cost distros, and made it ideologically unpalatable for other distros, and *BSDs.But the code is available now. You can take a look, compile it, give it a spin.