Even if half the volunteering recorders and their gear were as good as those of the commercial offerings, just sitting and selecting those that are not good enough for publishing and those that require some re-recording is a massive extra work.
I've listened to a few Librevox recordings. They're usually (though not always) tolerable. Occaisionlly good, but that's exceeding rare.
Good audiobooks -- and a friend listens to many -- are far more often vastly superior. Even then, a poor reader is exceedingly grating.
Libravox may improve with time. History of volunteer efforts has been compeling. But not yet.
I'm impressed by what librivox has achieved with just volunteers, but the production values are nowhere near as high as most books on audible.
IMHO they are just doing injustice to a number of good readers in their catalogue who put real effort into their recordings, but get buried under those one can barely listen to.