Ruby and PHP are easier for designers to learn and give them their first successes quickly. That's why they have prettier web sites in front of them. Maypole, Catalyst/Catamoose/Cata-what-have-you, Jifty, Mojo, or any other Perl framework you might be building next month are not going to make Perl more accessible to the brains of designers or give them their first successes anywhere near as quickly as Rails or PHP.
If I were going to try to get Perl into that niche, I'd think more in the direction of pushing something like Template to the point at which it can do everything a designer might want (database connections, sending email, etc.) without any need of serious Perl knowledge. Maybe from there the designers could be lured into learning Perl to do more serious stuff than the extended Template would be capable of. But the extended Template would have to be every bit as simple as Rails to get them that first success quickly.
It ain't about how pretty a Perl "website" [sic] might be. The pretty comes from the designers, not the language.