It takes about 1h 20m to fly from London to Glasgow and you generally need to be at the airport a few hours before plus there’s probably 30 minutes delay getting out of the airport on the other side. So you’re probably looking at only an hour shorter effective travel time for the plane.
Then if you consider how much of that time is stood in a queue compared to sat in a seat on a train where you can be working on a laptop and I think that rail travel is probably the best option for them a lot of the time.