The thing is; if your software wasn't offered for free, nobody would use it because someone else would offer their alternative for free.
Also, the most difficult problems which software solve are hidden problems. Sometimes critical, but hidden nonetheless. Nobody cares about system failure, at all, until it happens to them.
No matter how good your software is, you can't effectively market it as "reliable" because every single piece of software ever created in the world claims to be realiable even though almost none of them are! The label has lost all of its meaning and hence, cannot be communicated.
So this means that far worse competitors can gain adoption and take the entire market from you if there is any friction at all between the user and your product. Open source is an attempt to reduce friction as close as possible to 0.
Anyway this creates a hyper-competitive environment. If you don't have a voice in the economy, open source can seem like your only option to gain any adoption at all. It's a business model born out of desperation, not out of choice.
> if your software wasn't offered for free, nobody would use it because someone else would offer their alternative for free.
That suggests there's never been a viable market for commercial software at all, which is obviously wrong.
The label has not lost its meaning. Everybody knows what it means and wants it, just almost everybody “selling it” is claiming it without regard for the truth of their claim for their own financial gain. In polite society that is called lying and fraud.