I've only taken a return domestic flight once, donkeys year ago. I think it was London Edinburgh.
We don't do it much - we live in the Midlands, my parents live in the south west and my eldest lives in Scotland - it's usually her coming down to us and then returning home.
The reason we/she chooses to fly is cost/convenience/safety: cost is obvious, even just a week in advance, convenience is while she may have to sit around an airport for two hours, the flight itself is only 45 minutes or so, and the whole collection/drop-off thing
happens to be easier for us because it means not having to go into a city centre, and the safety thing is that she's a pretty 16yo traveling on her own, she's had one or two problems with people on trains, but not on planes. She, like me, has also had the dubious pleasure of being sat on a broken/stuck train for several hours.
Personally i prefer to drive - it takes longer, but I have control: if the motorway is closed I can decide to take an alternative route and which one, I can decide at any stage that I'm not happy with the road conditions and stop, turn around and either go back or find a hotel - with both a train and plane those decisions are in the hands of other people, and I can't get off of I disagree with them.
If trains from the Midlands to Glasgow took two hours, cost £100 return, and didn't sit near Carstairs junction for three hours in the snow with no heating I'd very happily use them - I could read, listen to podcasts, not have to worry about what that fuckwit in the Audi with no lights on was going to do...