That's because the geese you hunt haven't received the memo stating it takes at least a 3 1/2" shell packing close to 2 oz of HD shot to kill them.
They are still going by the old rules where 2 3/4" shells were all there were other than muzzle loaders. Of course they were allowed to be killed by muzzle loaders as well.
Just be happy they missed the memo or you will have to go out and buy a 10 ga. and cases of 3 1/2" shells.
I hope the ducks I kill each year with my 20 ga don't check their email or I'll have to switch to a 12 ga.