Apple DOES care where it is installed and under the Constitutional law, Apple gets to determine how their hard work is put to use. They limit where it can be installed in the license. Federal law says that is OK. Apple owns that software and they are merely giving you a limited permission to use it. You are NOT buying the software, just that very constrained, limited permission.
Microsoft makes billions of dollars for selling their OS. . . Apple does not.
Apple was required by accounting laws to charge distribution costs. That is why the $19.95 was charged for the media. It did not provide a profit. Now Apple provides it free because the accounting rules have changed. GAAP no longer requires it for downloadable software. OS X upgrades, even major revisions, are free to Mac owners.
I think the whole 'license' vs 'purchase' stuff as it regards software t be a steaming pile created by control freaks who don't really understand the difference between me using a personally purchased product as I will and someone cranking out copies for anyone who wants one.
Apple generally does not go after hobbyists who make Frankentoshes. . . but they are within their rights to do so. They have found over the years that most find the exercise frustrating and generally eventually buy a legitimate Mac.They only go after those who try to monetize the practice.
I did think as you thought at one time. . . but then I rethought it after a friend of mine spent $30,000 and ten months of his time developing a classroom management tool for the old Apple II. It was the most popular tool of that type. He sold exactly 347 copies. Why? Because school districts bought one, copied and distributed to their classroom teachers without buying licenses! Whole STATES did that! An Apple magazine picked it up and sent it out on a disk free of charge as freeware, without attribution! It got passed around from teacher to teacher. What was he charging? $20. He lost his shirt!
Again, someone has to take a stand for what is right. Laws about how many rounds in a magazine are wrong. This is not like that.
Your friend who got screwed over by the schools is a different case IMO, those school districts were just being typical liberals, and stealing what they could get away with. I think I'm the only person I know who had an actual legitimate, licensed copy of pkzip back in the day. These days, there is little reason for me to purchase any software, though I would if there was something compelling that I wanted to support (kinda like FR in that way). For instance, I gave money to 'YouVersion" because I really liked their Bible software and their mission.
I just really dislike the entire concept of licensed software in the way that Apple means it. Guess that's why I'm a Linux guy rather than a Mac guy. WifeofZeugma really likes her Macs, but I'm more hands on.
Even with Linux, I'm not opposed to paying for perceived value. Hell, years back, I used to subscribe to a fellow who produced and mailed out RedHat disks with all updates on a monthly subscription model. He wasn't making much, if anything, and I could have easily spent the time necessary to download the ISOs myself, but I really liked the convenience of it.