Well the largest advantage is you can write and test scripts on Linux that will work on UN*X (like AIX) where bash does not exist. Also this works:

awk '{printf("%s %s %s %s", $1, $2, $3, $4)}' < file | read v1 v2 v3 v4

and many ksh scripts outside of Linux uses that syntax

What does Korn Shell offer over Bash shell, again? I've never used it, other than encountering a few legacy scripts on customer systems written in ksh that stopped working when they migrated over to RHEL/Centos7 and ksh was no longer installed by default.