One example: In my country, Windows is std de facto OS, because no one pays for it. If it weren't available, no one would use it. i.e. it is not a loss for MS. It is actually advantage, because MS can enforce govermental or commercial structures to pay for it.
Now, to rephrase the question, if you worked for a year on something with the expectation to sell it, would you be happy to see it "shared" freely by others?
Also, we were told that sharing our stuff is a good thing -- not that sharing other's people stuff aainst their will is a good thing.
I'd never refuse to anyone asking to share a copy of some mp3/dvd/software or any other type of copyable thing, even if I paid for it.