Oh wasnt meaning to come on strong, sorry if it seemed that way. That's the problem with non verbal communication, too much is lost. It prevents the glass from cracking because it evenly distributes the downward pressure of the aquarium and it's contents onto the stand, instead of having pressure points. Imagine those matress commercials that show pressure points on the back, it's quite a bit like that. Now when you have localized pressure points plus harmonic motion like an earthquake or even a person walking by without a care (fairly unlikely), the glass can break. That little bit of foam distributes the shock of harmonic energy throughout the bottom of the tank, instead of to specific pressure points creaded by surface imperfections in both the aquarium glass and the stand top.
I mentioned the walking thing because it's the same principle, though walking is much larger scale because there are quite a number of shock absorbtion systems built into our body, incluting the arch of your foot, bent knees, discs in your back, your glutes, calf muscles, to name a few. But the brain and optic nerve are quite a lot more sensitive than some aquarium glass
This came to mind because i remember a guy who had several vertebra in his back fused and started having problems with headaches, and noticed pronounced vibration in his vision when he stepped. That would suck!