True, we should care for newbies, but we should have the good of the project at number one. I can't find a single policy that we don't need (can you?). Policies we don't need probably won't get promoted to policy to begin with.
Even if you can't point to a policy page and say "we'd be better off if that whole page were deleted", it seems to me that after promotion to policy level, the process of annotating and expanding that policy happens slowly, under much less scrutiny, and at a much lower threshold of acceptance.
I have in mind WP:U. The general idea -- no offensive usernames -- may be good, but read all of the fine print that has accumulated over time. Do not think this is idle policy cruft that nobody acts upon. Newbies now get instantly and permanently blocked for what in my opinion are really stupid, arbitrary offences.
Perhaps WP:U is an extreme case, but I suspect something like this happens on many policy pages, and never mind guidelines.
Dan