That’s where you and me and the millions of HTML/CSS coders out there come in. Theme development is the last thing I would want the BuddyPress team wasting their time on. Their limited development resources need to be focused on functionality. As besides that… the default theme is already pretty awesome if you ask me. If you want to see an ugly default theme (that is impossible to redesign in a meaningful way)… look at Elgg. Ick.
There are already good themes for buddypress. I guess you haven’t searched enough. Core teams should focus on development, not themes. Since 1.1 theme design got much easier than before, so any wordpress theme designers can design.
I’m sure that within the next few years there will be a ton of BuddyPress themes out there. It’s just too new right now. 1.1 just came out last week. But it’ll happen. Just look at the millions of WordPress themes out there. And all those theme developers can “hit the ground running” with BuddyPress. Especially with 1.1… which is much simpler to theme than 1.0. Doing a BuddyPress theme is basically the same as doing a WordPress theme… just with more templates (Profile, Directories, Site Activity, etc.).
Also, it’s only natural that the first few themes available will be pretty simple re-workings of the default. Again… I think it’s just a matter of time before we start seeing really different high quality themes… like with WordPress. Elgg on the other hand will probably never had any good themes because it’s next to impossible to theme. Every Elgg theme I’ve ever seen is just a simple (ugly) re-work of the ugly default. That won’t be the case with BuddyPress.