The need to earn money also incentivizes people to work on products that are monetiziable. More specifically, it encourages people to move their project in a monetiziable direction which puts the priority on revenue generation over quality.
It's also possible to create content that's more experimental and creative, by focusing on more niche audiences. This is evidenced by the current golden age of TV and streaming, with a wide variety of dramas, comedies, documentaries, etc.
So, a product for which people are willing to give you money in exchange. People are not likely going to buy a shitty product unless the situation involves monopoly (natural or otherwise) or regulatory capture
On the other hand, the need to be able to sell things means the quality has to meet the customer's expectations.
For example, cars produced by free market companies far exceed in quality those produced by socialist operations.
In fact, I suspect you'd be hard pressed to find any examples of anything people made purely for their own amusement being better quality than items they made for sale.
For example, the software I write for my own personal use tends to be pretty slipshod, as it only has to work for my use case. I don't bother with coherent error messages, documentation, a decent user interface, or fixing any bugs that don't directly impede what I use it for. Doing that stuff is simply not worth my time unless I'm planning on distributing it.