I agree, however a few years back a product came out which was essentially an insert disc ( which looked like Styrofoam) to put inside Styrofoam cups, it had some thickness and a very hard core, the idea was to have these discs inside the cups as a backup. If the wrong cup was hit, the hard core of the disc prevented the nail/knife from penetrating the bottom of the cup. The effect would be ruined but your hand was saved.

I only saw the product a few times and don't remember its name I also haven't seen it since, so I guess it was never adopted by many.

Having said that, I agree that there are better and safer versions than the ones using knives and or spikes.