On flagship phones, it sure doesn't seem to be common.

GS4, iPhone5, Nexus 4, Nexus 5, HTC One (Horrible offender here).

If you get an 8/10 on iFixit, you have about the most perfect score possible with top of the line phones.

Previous generation of phones could replace glass without replacing screen.

Easily the worst thing about the iPad and the iPad Mini is the huge air gap between the LCD and the cover glass, which reduces clarity and makes glare much worse. The big plate of glass in front of the LCD is something I appreciate for say the iPad my daughter plays with, but for something I actually have to look at give me a fused display any day.

The tradeoff being subpar outdoor performance, viewing angles, and touch accuracy.

Only on devices with glued glass. Of course glueing it on the rims and leaving a huge air gap would do all that.

if you do decent product design instead of copying every bad decision apple made, you'd have the glass framed. It would have no discernible air gap. all the things you said would be just as fine. and it could be replaced by removing the frame, probably with screws.

but no, let's use corning glass (with lots of impurities so it is crack prone but hard to scratch... the perfect glass to be framed) and use it on the whole front of the device so it is guaranteed that it will break if the device falls.

sometimes i really wish apple had had it's way on the illegals claims about owning design elements. we'd at least be safe from their bad choices.

If you don't fuse (glue) the glass to the display, and don't leave an air gap, the result is an easily-damaged screen as the glass sheet rubs the LCD. Framing the display would change nothing about this equation, and the decision to use Corning glass has nothing to do with optical fusion.

Just about the only downside to fusing the display is repairability.

if both are equally secured there is no rubbing.

and yes i know corning glass decision is only because it does not scratch.

my main point thought is about extending a fragile glass like corning to the corners.

It seems to me like many phones are going the fused glass and LCD route these days, so it's getting harder/more expensive to replace the glass and/or LCD.