I disagree with your numbers. For a short trip like DFW-HOU or DFW-CRP, I find it takes 2 - 2.5 hours for me to get from my home, fly, and be en route (via taxi or car rental) to my destination.

But let's assume your numbers are correct. I do live only 15 minutes from DFW airport. The extra 70 minutes you save by flying is actually doubled for the round trip, so it becomes nearly 2.5 hours of extra productive time in the middle of your workday.

I can fly DFW-IAH round trip easily in a single day, and have a nice long meeting in the middle. Leave the house at 7:30 for a 9:00 am flight, meet from 11 am to 4 pm, home by 6 or 7 pm. Less than a 12-hour day, and that assumes a 5-hour meeting. Plus it's easier to sit on a plane for an hour or so, where I can sleep, eat, or work, rather than concentrating on driving for 4 hours.

If I drove, I would leave the house at 7:30, hit Dallas traffic, drive 4 hours, hit Houston lunch traffic, two hour meeting, drive 4 hours and probably hit Dallas traffic again. I consider the uncertainty of driving in traffic to be equivalent to the uncertainty of airport delays.

In either case, I shouldn't have to include the possibility of a government agent groping me or seeing me naked as part of my calculus.