The market has spoken in terms of preferring free tools. I personally think that is one big reason why the quality of developer tools is as low as it is.
For some reason the equality seems to hold for most applications with a complex user interface. Reasons may include that it is a cross discipline thing that requires skills/people such as interaction designers, artists, technical writers, linguists etc that are less common than developers in the OSS community. It could also be that good interface design benefits from a centralized decision process which can be a bad fit for OSS that is usually too incremental and democratic for radical design changes. Normally there is no money for things like paid UI testing/focus groups.
That said, there is great free software with good UI/UX too - only they are more or less always backed by a large corporation.
A market with only free offerings will cause a certain category of actors to be absent. I would think that a market with fewer categories of actors would correspond into a drop in quality among some dimensions.
