When you have advantages that often come down to "it works great on a teletype over 150 baud" (read, compressed syntax, regex, etc) you will eventually be beaten by something that is easier to read at a glance.

Non-programmers read python and sometimes even Java and say "huh, this is something that could be figured out" - reading perl was reading line noise.

APL is probably one of the most powerful languages out there, but the characters in the syntax scare most away.