Re: Wouldn't it be nice ..
These glass slabs aren't slippery if you put them in a case. A case will also solve your protruding camera lens issue. As a side benefit they identify your phone as yours, just in case your mates have the same model.
Some phones have sapphire over the camera lens; if it's scratched then it's likely due to jewelry or diamond cutting discs (or the dust after using them) that's likely to be the culprit. Blow or brush the camera lens before wiping it on your shirt.
It's healthy to suggest that certain design choices are questionable as long as one is genuinely ready to hear possible answers. I understand that a protruding camera lens prevents a naked phone from being laid flat on a table, but I also understand it provides a tactile aid to help obscuring the lens with one's finger, and that anyway most people use cases. Some people would say that nudging people to place their phones face down is also socially desirable. There has been a choice, all options have been questioned, and the pros and cons weighed up.