Answer:
When you've removed the tradition, elitism and semantics often involved in this issue, you could argue that be simply by placing the ability to produce images in the hands of the masses, digital photography has allowed otherwise unreachable brains to experiment in the medium.
While it could be argued that monkey-friendly typewriters aren't going to produce Much Ado any time soon, there are always those on the periphery worth considering.
In addition to this, there is a historical reference worth considering. Digital photography isn't the first time that photography has been taken out of the hands of the the few and placed into the hands of the many. In 1900 Eastman Kodak produced a $1 camera (including film), up until then, cameras were expensive and developing the images tricky. The result was a huge increase in the number of photographs being taken - this created a distinctive style of photography (the snapshot) which echos still today, and acted as an important record of that period of time (see Joseph August Lux Künstlerische Kodakgeheimnisse).
So to summarize - Digital photography has improved the quality of photography, through accessibility and proliferation.