[plt-scheme] Why is Planet better than PLT archives?

Now I've got a question too.

Why must one use (require (planet ...)). Why not make
a more intelligent mechanism, using (require (lib ...))?

I also noticed that a plt package for --all-users, when
installed with 'planet --file ...' will get installed in the
plt scheme system collects directories.

And, what, if there's no internet connection? At my
work I noticed that (require (planet ...)) will yield
an unrecoverable error when not connected to the
internet, which I think cannot be acceptable.

Best whishes,

Hans