To SKRIDLOV
Yes the data is available but its' accuracy will depend on lots of factors. The accuracy of these scales can vary by terrific margins (handy hint if they try to charge you excess-use other scales). They may sometimes be calibrated but I have no personal knowledge of this being done.
These scales are subject to enormous wear and tear, dust, being moved about etc. all those fairy light staff jumping on them to see how much weight they have lost.
In other words they are not particularly accurate, and I for one would not like to see them used in a final weight and balance sheet.
The cost of what would have to be done to ensure their accuracy would not be welcome in a business cutting unecessary costs to the bone.
It is mooted that for smaller aircraft, less than 20 pax, the weighing of both the pax and the bags may be useful.
Then of course we get into discrimination etc..and lawyers involved.
As usual things ain't never as easy as they seem to be.