Now that is funny.
If the airlines measured the real pax+baggage+carryon weigh they could then maximise their freight load, but only after taking in to account the captains view of how much fuel to take for the trip + Wx + probable delays.
If the airlines measured the real pax+baggage+carryon weight then they would prove something that they actually already know. Their aircraft are overweight!
Major ripples through the industry with airfares jacked up 10% overnight.
I agree that the technology is available, just as it is for oleo based on aircraft scales. There is no appetite for this for commercial reasons but remember everyone SAFETY FIRST and SAFE SKIES FOR ALL.