But what you mentioned absolutely happens, though.

It’s €17 to go to the Louvre. Many of the paintings there are public domain, which logically says they should be free as they have no owners. Yet to see them, most people need to pay €17.

Those are paintings locked behind a paywall. The pieces may be donated freely by an artist - just as users contribute freely on a website - but the museum still charges for admission.

So while I’m not defending the practice - and there are many free museums; even the Louvre has ways to get in for free - it’s also not exactly a way to convince others that the practice is inherently bad.