In Europe, §1.620
EU-OPS Subpart J tells us that 75 kg is only close for holiday charters >30 seats. Otherwise, it is low.
In the US, 75 kg equals 165 lbm and is, again, low. The official word comes from
AC120-27E and states 190 lbs for a mixed pax load in the summer, 195 in winter. Without carry-ons, the summer weight goes down to 184 lbm.
The standard weights are determined by weighing pax and bags and applying statistical methods. They are revised every now and then, although chances are they are not revised often enough.
75 kg will probably only be valid in Asia these days, where they are blessed with significantly lower average pax weights.