often seen in the street without a hat

That's one reason (and a damn good one). And the fact that she loves to entwine her hands in long hair, and her hands are grubby and grabby. Also, though, lots of my hair started falling out when Naomi was a couple of months old (apparently this is because it doesn't fall out while you're pregnant and so there's some catching up to do, and you don't actually go bald. But it's still a bit alarming.) and it's easier to deal with when short.