I once spent 2 weeks on an aircraft carrier. After a week of morning met-briefs, I finally worked out by the Royal Navy didn't give QFE. I suppose I was young and innocent then.
I'm perfectly acquainted with the QFE/QNH debate, it's one of those old chestnuts that'll never go away - but causes mild amusement with visiting North Americans. But concerning barometric pressure - what else could you use? Radalt is too expensive for simple aircraft and doesn't work at altitude or whilst manoeuvring, temperature is too coarse and varies too much at S/L. Just as Churchill said about democracy, pressure altitude is perfectly awful, but better than all the alternatives.
I suppose now we have the geometric altitude given to us by GPS, but even that we'd have to be careful about since the world just aint that round, and the update rate on GPS isn't really up to aircraft manoeuvring anyway.
G
(N.B. Idle stop, I think the correct answer is go to the Janitor and say "if I give you this nice barometer, will you tell me how tall the building is").