The problem is that the drivers will not respect track limits. So they put in physical barriers, and then you get unforseen consequences like launching cars into the air, or bouncing off fences. The FIA have to make it totally against the drivers interest to go off track, and if that means more cars not finishing because they are stranded in a gravel trap, then so be it.
Gravel trap is not needed as you only need them to slow down a car before it hits the barrier. When drivers run slightly wide they drag lots of gravel back onto the track.
You need a punishment mechanism for running wide. Grass will just cause more crashes and whilst sausage kerbs do work they can break cars and obviously launch cars.
I think they should just have 2 second time penalties every time you breach track limits.