Why don't we change our traditions and bury people vertically?

We have done it in the past. We no longer stick you up on a scaffold or build a big bonfire around you. And, if I am not mistaken in Europe in the past your family had to keep paying for the plot otherwise they dug you up and put what was left into a charnel house and resold your old resting place.

Figuring a 3×3 rectangular plot for a 30” diameter shaft, you could bury approximately three people in the space now reserved for one. We do it in a horizontal format in Mausoleums.
It would be a lot easier to get a pier driller into and out of the cemetery than that ol’ backhoe they use now. Dig a 10 deep hole, slide in that cylindrical coffin and boom. Easy backfill and settling repair And, you could get some very nice round tombstones placed level with the ground to facilitate easy mowing AND they can be placed to make a very attractive stepping stone walkway.
No one (or very few anyway) care anymore about whether they are facing East to watch the rising sun. And we all know they are not really “sleeping” so don’t need to be on their back.
So, why not?