I think I answered the question with the title of this post, but it
leaves me wondering why Oracles upgrade assistant only works if the
database you are upgrading from is on the same machine. I know MS-SQL is
a different beast, but it does effortless upgrades from one machine to
another and the basic premise is the same, except in Oracle you are
moving many schema's over while MSSQL is moving one schema (database)

Or is there another reason Oracle can't do this? Normally exp/imp is no
problem as the ones I have done so far are relatively small, but I am
doing a bigger one now (still small by database standards at 20GB) and
it is DOG SLOW, 2 hours so far and it's only part way through the first
of many schemas I am moving over.