Lloyd answered your question about including wp-cache in core pretty well, but I wanted to add that the last time it came up in wp-hackers (mailing list) the conclusion was that there were enough people running systems that were better served by other methods at the server level (memcache and other server tweaks) and enough people who for whatever reason would be unable to use wp-cache that it would just add bloat to the system to include it in all WordPress downloads. There were a few people who were pretty upset at the idea actually. Like you said though, 99% of users with shared hosting should turn it on, especially if they are installing all the other plugins you guys recommend!

if there’s a great design /layout that people can choose from, pay something nominal that supports great designers and contributors to the community, I don’t see the problem.

Fixed. I think it had something to do with permissions being wrong.