I think that this is one area where there is discrimination against Y class pax.
When I travel on business, I can get away with murder on hand baggage and the checked luggage allowance is 30kg on the ticket, with usually another 10kg from my FF card.
Yesterday, I took three flights in J/C, with 2 pcs of hand luggage that were undoubtedly over the ticket limit (but within the overhead bin parameters, considering their volume) and no one batted an eyelid.
I would not try to do the same in Y or on loco, I would even weigh the bags before leaving home to ensure I was okay.
As another poster said, some middle eastern airlines are pretty good, with a 30kg allowance in Y.