My guess is that they were being asked by bloggers, journalists, etc who were coming in for SXSW and thought it would be easier to put out an online statement to direct people to.
I don't think this is a high priority for APD.
I don't see the big deal really. I've lived in Austin since 2005 and I've never used a cab service here. They seem pretty useless in this city IMO.
I should also mention that I'm not a fan of Uber. I've been with friends and coworkers using it in San Francisco and always I see 3-4 available yellow cabs go by while we wait for our driver.
I'm in San Fran 1 week a month and when I'm by myself, I just take yellow cabs. They seem to work OK for me.