The thing is that it just isn't that obvious.
Not one cell before Apple's iPhone had swipe to unlock. Not one cell had touchscreen that works without stylus.
Same thing with tablets. Sure, Microsoft started making them long time ago but using styluses on the same GUI was not that practical. That's why they never entered mainstream market. iPhones and then iPads brought new GUI for whom you didn't have to use styluses and you didn't have tiny unclickable icons. Everything is made for touching from the ground up.
Sorry for going off topic.