with my Ibook I couldn't install other OS on working conditions because Apple wouldn't just open the specs, so there wasn't really other OSs to install. It is also not really an option to install other OSs on the IPad. And it costs a lot of money, that makes a big diference. You pay to be locked in to Apple.
Then when Samsung comes around and offers almost the same features, people start to worry that their overly priced stuff will not be so special anymore, and act like Samsung's products are just a poorly made ripoff.
It was years ago so I don't recall the details but it was definitely possible and not terribly difficult.
If you want a challenge, try installing Arch on an 12" PowerBook G4. I spent three days one winter break in college getting that on there.
The only time in the Mac's history that Apple wasn't working to make sure it could run Unix was 1984-1987ish before they released their flavor of Unix.