Well the reason you can is because you're not in the air, basically....
Towering simply types ".ef" for you. If you're on the ground and moving below 50MPH (or whatever the rolling exit limit is) you will tower. Well works great in planes. Works better in GVs. You're always on the ground. And you always are going less than 40mph (almost always??).
Not a bug. A feature. Ground crews can exit craft easil.
HOWEVER, I would LOVE to see the "tower" button isolated. Put a blank space under it, then continue with the menu options. I've clicked it too many times, as well.