We considered it, but for now it's not a big priority. Yes, the default look is boring, but changing it is a huge undertaking. MediaWiki code is intertwined with the way it looks and there are a ton of gotchas here and there that would require a lot of work to iron out.
Other skins might looks alright on the surfaces, but there are a lot of edge cases where they don't handle something fully, and things will break on updates, etc. Not really worth the effort at the moment.
But something that might make more sense would be adapting the default skin to something that looks better.