"As I said, my school had dual Linux/Windows systems in the labs for teaching both."
... ah, you DO understand that the overwhelming majority of professions in this world, although many use computers, need absolutely NO knowledge whatsoever about how they work or what type of programming they require, don't you ?
UMIX is there for those who want to learn it as part of a CS course. It is also likely to be used by engineers, since UNIX is still popular in that field and they often have to write their own applications. Our best programmer here doesn't have a CS degree, but an engineering degree, and he's a UNIX guy. Cliff Stoll was an astronomer by trade, but also a UNIX guru because he needed that to do his job.