Majority of people using 16:9 monitors are actually people who connect their consoles to it (PS3/360).
Because both consoles do not have an aspect ratio scaler, that means playing them on a 16:10 monitor would make the monitor look stretched out.

While there is 1:1 pixel mapping on many 16:10 monitors, doing so would make games run in such a small window that it would detract the experience from a full screen play. This is because most PS3 games do not have 1080p upscaling support.

And yes, there are plenty of people who plays their PS3 and 360 on a monitor due to either having no space for a TV or a budget.

So IMO, 16:9 really isn't that bad to be quite honest. But yes, 16:10 monitors should make a come back into the mainstream market, no doubt about that.