Most 'cabin bags' are carefully sized these days to meet the regulations, and some have wheels.There are always people who take the pee 3 bags when 2 are allowed. Wheelie bags as under seat luggage.
Under seat luggage? When was the last time you flew?
Sure, it's an option, but most goes in the overhead lockers these days.
I believe handbags don't count, and are allowed. But obviously anyone taking the pee would be asked to do something with them.
Also duty free is allowed as extra.
Some airlines are weighing passengers, but it's a bit controversial.