Perl had the popularity Arc could have had. Then Python did, then Ruby.
I will point out that Perl still has the popularity. Python and, particularly, Ruby have dramatically fewer developers and lines of code than Perl. But, then, Perl has fewer developers and lines of code than PHP. So, unless PHP is the exception that proves the rule, the popularity argument is obviously moot. But, I do think there's something to be said for pragmatism. While Perl (or Python, Ruby, etc.) has its flaws, it also has a vast community of people working on solving them...will Perl 6 be ready before arc is usable for a similarly wide array of problems? Seems pretty likely.