The people who associate Seattle with rain and wetness should really visit during the summer. Everywhere you look, the grass has dried to a crunchy brown. Maybe that's why the old nickname of Emerald City has fallen out of favor. Then again, nicknames for cities are usually fairly misguided. Chicago isn't the windiest, and Kalamazoo has paved over its outdoor mall. People in Atlanta don't pronouce the "t"s so hotlanta is hardly appropriate. However, I think that it's best not to mess with Texas.
I guess it gives T-shirt manufacturers something to print and sell to tourists, so it serves the grander purpose of capitalism. Hurrah.