If the manufacturers will release the damn specs the geeks write the drivers for them and those drivers get included with every distribution by default.
While that is an interesting argument, there are a few fundamental problems that bother me:
a) The incentive of manufacturers to release said specifications is low. Regardless of money made on the acquisition of a wider user base (often through more hardware sales), such specifications create issues for intellectual property and often serve as an opportunity for any competing manufacturers to digest a well-prepared buffet of the inner workings of hardware and the software that supports it.
b) The incentive of said 'geek' to actually sit down and not only write but actively maintain said drivers is based on demand and free time. This leads to the parent post "now you see it, now you don't" support syndrome.
c) The incentive of a manufacturer to release quality specifications is next to non-existent. In many cases, only the most determined OSS master-mind is capable of both understanding what are often meant as 'internal use only' documents and actually creating a driver. While I have little doubt such people exist, there is only so much time, sweat, blood, and tears that many people are willing to give for results.
Note that I actively contribute to the open source community and use Linux on a regular basis. That said, I don't believe manufacturers are (entirely) to blame.
"The one charm of marriage is that it makes a life of deception a neccessity." - Oscar Wilde