Do you even ran your code in place where bash wasn't available? I held thought like you... 10 years ago but that really doesn't happen and if it does, rest of it probably won't work either...
Yes. Alpine ash shell (the default),macOS zsh shell (the default), and Oracle Solaris sh shell (the default). The systems are enterprise regulated, so a typical user cannot easily install a different shell. POSIX works great.
