How come so many prefer the Korn shell?

What I don't like about it is that it's proprietary
though by now I think there is a public domain ksh available.

On some modern Unices like HP-UX there's no need at all for ksh
since the standard HP shell is a Posix shell with much of the capabilities
of Bash or Ksh.

If not on HP however, I prefer Bash.

But even though Bash offers arrays, and arithmetics and many other
neat stuff,
I find as soon as I feel it would be handier to have LoLs or more advanced
data structures that autovivicate on the fly,
simply to avoid temporaral dump files or awkward evals,
or if parsing gets too circuituous and involves too many pipes,
I pretty soon end up doing it in Perl.

So no doubt, Perl is my preferred shell.