I will give you a reason why this might be useful. Not at Gatwick. (I always took the train when I lived in that area and usually ended up at Heathrow or Stanstead anyway). But at Raleigh NC for example, you have to go up 5 levels to find a spot, (I have never seen an open spot on levels 1-4) and spend about 10 minutes or more finding a spot after that, then walking from your spot to the elevator, then back out. Or sometimes the lot is filled up, and you have to drive to a lot far away, then spend even longer finding a spot that will be at the far end of the lot, then walking a good distance to the bus terminal.

That's if you know the system, and are aware that you won't find spots on the lower levels, and that the "x spots open" indicators are lying. If you're new, you can spend 30+ minutes on a goose chase, miss your flight etc.

This solves that problem; not the bus one. (If the drop-off location is easy to access; if not, then it's pointless)