I lived in the Houston area for nearly 35 years and have yet to find someone who has taken a flight from Hobby to IAH. I have known a few people who have taken a shuttle bus between the two, but they all have said it really wasn’t worth the time and trouble. I’m not saying it’s never been done, it’s just not a popular option.
It really depends on the traveler, where they are going, and whether or not the delay is going to add an extra day to their travel. By sending the re-routed flight to an out-of-the-way airport, it pretty much takes any choice out of the hands of the passenger.
That’s my point. They aren’t going to end the practice of code sharing as it benefits both airlines, but they can limit how much of it goes on due to weather diversions by judicious selection of the airport the diverted flights are sent. It would have cost them less in fuel, less in labor costs, and less discomfort to the passenger to go to either Austin or SA, but they made the decision to fly an additional 200 miles. What do you think their motivation was?