I personally can't think of the last time I wanted to open a laptop 180* or more.
Obviously both our experience is anecdotal but if it was driving purchasing decisions you'd see more laptops that can open 180 since the design trade-offs are relatively minor in the overwhelming majority of cases.
On a plane is pretty much the only time for me. I've been on planes where my intention to get work done on the trip was shot because with the keyboard on the tray I wasn't able to open the screen far enough to get a good view.
But typing on a vertical keyboard is probably not awesome.
Obviously both our experience is anecdotal but if it was driving purchasing decisions you'd see more laptops that can open 180 since the design trade-offs are relatively minor in the overwhelming majority of cases.