I suppose the same reason why qwerty still reigns supreme despite being a purposefully inefficient layout, people know it.
On a similar note I was talking to someone recently about touch screen phone keyboards, and how compressing a qwerty keyboard onto a (relative to the size of actual keyboards) tiny screen with very little haptic feedback seemed like an awful idea that was used early on because it was easy to understand and since then we've just kind of stuck with for no reason. The person I was talking to agreed, and we were thinking of ideas of how it could be improved. Later I was talking to a my two brothers about it, who are more a bit more normal, and neither of them thought it was worth the effort at all (and they're probably right), and thought it was pretty daft thing to care about.
Long story short, if it aint broke, don't fix it I suppose
I was very pleasantly surprised to find that my muscle memory for "real" QWERTY keyboards works on touch keyboards as well. I know people who can "touch type" (as in, without looking) on touchscreens as well. I doubt anyone would be able to become so adept if the layouts were different.
I can recommend the typewise keyboard. The keys are hexagonal and you use gestures to delete, restore and uppercase letters. Therefore you have bigger keys for the same amount of screen space. It's not QWERTY, but the keys are in the region of their QWERTY location (i.e. not something totally different like dvorak). I needed some time to get used to it, but I really like it and don't want to go back.
I think it's pretty daft to not consider an investment (by all of humanity, which I get is hard) which can improve efficiency by a lot, for all of time until we direct BMI.
At some point in the sliding scale it becomes worthwhile to care about and implement
On a similar note I was talking to someone recently about touch screen phone keyboards, and how compressing a qwerty keyboard onto a (relative to the size of actual keyboards) tiny screen with very little haptic feedback seemed like an awful idea that was used early on because it was easy to understand and since then we've just kind of stuck with for no reason. The person I was talking to agreed, and we were thinking of ideas of how it could be improved. Later I was talking to a my two brothers about it, who are more a bit more normal, and neither of them thought it was worth the effort at all (and they're probably right), and thought it was pretty daft thing to care about.
Long story short, if it aint broke, don't fix it I suppose