You've obviously never been in charge of the air fence like I was at Newcastle.. The idea of a 12in hole is neither practical or affordable.
AirFences serve different situations.
1 - Fixed fence, that can be left in position each week. Again two different scenarios. Fences that can be left like foam fences(Berwick and Glasgow) needing only cleaning between meetings, and inflated fences that are in position (Redcar) but need to be deflated and then reflated before each meeting. In each case, it is beneficial to cover the fence with advertising and plain banners which are much easier to clean that the fence. Only need to spray the top and the skirts of the actual fence.
2 - Detached fence where, after the meeting, they have to be deflated and folded, and then inflated and attached to the fence by hooks(Newcastle) before the next meeting. The reason for this is that the Stadium owners insist on the fence being dropped, so that the doggies punters can see their legs when the dogs are racing in the outer track. Again you should need banners to make fence cleaning easier and minimised.
3 - Moveabable fence, where the airfence is in front of Armco metal fence for the stocks racing (Scunthorpe), and folded over the back of the Armco for Stox meetings.
4 - Remove the fence totally like I believe Sheffield have to do, to accommodate the requests of the stadium owners to satisfy the dog owners. Why would happened to the hole then ?
As you can see there are differences, and the suggestion like digging the 12 in hole for the airfence is only a possibly a runner in situation 1 above, but the cost of the airfence would be considerably enhanced, but for what improvement ?
In situation 3, it would be impossible to run the stocks with a 12in hole in front of the Armco, as vehicles would lock their front wheel in the run caused a crash when previously the vehicle would just glance off the barrier and continue racing.
In situation 2. the hole would fill up with rain water which would have to be removed to insert the airfence, and which would be extremely messy, more messy than it is now. That water would have to be lifted to go somewhere, and during the week there is the possibility of the water ingressing into the track, and then making the track preparation difficult by having to squeeze the water out in order to deliver a uniformly water track for the next meeting. What happens if the edge collapses ? Again the extra cost the larger airfence would be considerably enhanced with no benefits, but great difficulties for the fence erectors and the track curator.
No doubt you will repeat your opening sentence again in a years time.