I bought a clear shockproof protector for my telephone screen today. I'd already had the screen replaced once, and I know so many people who walk about with telephones that have cracked screens that it seemed a good idea, especially for someone who is as inclined to trip over and drop things as I am.
Afterwards, as I was sticking the thing onto my telephone, it did occur to me that it might be more convenient, if less lucrative for the telephone manufacturer, if they simply made the screens shockproof to begin with.
Is the fact that they don't really a mystery though? It depends how cynical you are, I suppose.