Let's get a little perspective here from an operational standpoint. While I don't agree with keeping the customers out off a gate for long periods, you need to see what happens in these kinds of situations.
As a former Dispatcher, I've been working on hand have seen days when weather blocks routes into your hub airport or shuts down a major airport. It's an absolutely, frustrating nightmare. For lack of a better way at the time, we'd keep a whiteboard list with which airports were available and how many our station personnel could take (whomever wasn't working the hub or swampped would normally take care of this). Once we diverted flights to that station and it was full, we'd stop sending them there, if at all possible. Now you have to imagine that all the other airlines are doing simliar operations with their planes.
In an airport like AUS or SAT, where there isn't really a dominant airline, it's difficult for a station person for your airline to see what the big picture is at the airport as a whole until it's too late; aircrat are left without gates and the ground holds/delays are at a maximum.
Knowing ATC and the weather in Dallas and in central TX that particular day (I live in the DFW area), there were multiple ATC ground stops and ground delays going off and on all day. There may not have been an open route between AUS and DFW for quite a while. The Crew was probably told numerous times that they had a slot time, but then it got cancelled for new stoms that developed or moved in/near both airports. It happens. The fuelers were probably buried with refueling all the diverted a/c and all the a/c that were already on the ground for regular operations. Airstairs, other than on the aircraft itself, may or may not be available at all stations.
Again, I don't agree with letting these people stay on the plane for as long as they did. Good customer service in many departments of the airline would have/should have found a way to make the "imprisonment" a little more bearable. There were things that Dispatch, Maintenance, Customer Service or even the Crews could have probably done, depending on the legalities and the information each had at the time. Any one of these teams/departments could've made a small difference. Finger pointing and blaming "management" (who is completely out of the operation on a day-to-day routine) isn't going to make anything better.
On days like this, everyone should make an effort to do what they can and COMMUNICATE what's happening.
Management's job is to get involved after the fact in customer care and in trying to find a way to better manage recovery efforts when a hub goes sour for weather.
Vent over.