(I secretly also enjoy thumb holes them for their intended purpose + coziness)
They're designed to end halfway down your hand, and for some of us, that makes them the perfect length (though it can be uncomfortable in the webbing of your thumb if you instinctively put your thumbs through when there isn't actually enough length for that).
(And since you’re here: I find that men’s slim long sleeve shirts at banana republic fit well on sleeve length for moderately tall slender women—my XXS flannel is great, though a touch tight when all buttoned up)