imho the default themes should be created in the way CSS Zengarden worked: you have a solid base (before it was _s, now we need something new) and then you show people, how this base can be made into something.

You do not invent a wheel once again, but iterate, iterate, improve and build on previous core, so people could clearly see the process and how new features are being implemented into something that was working before.

When the time comes for a new theme, you iterate again, and, because the core is the same, you show people what you did to improve the functionality of theme, etc. Previous themes were educational tools, now it is hard to learn from them, because you don't see how it was done - every new theme comes from different developer, follows different thought patterns, etc.

I have built Tiny Framework theme with this idea - I took the default theme and showed people how to extend it. It is still used by 7k sites, but now I cannot do this, because there is no good base theme...

Just saying...