Maybe the boot tree entertains the Kea birds and keeps them away from tearing up tents and other belongings. Just a thought.
You often find them hanging out near the snow line, and they can wreck the fittings on a car in a matter of minutes with their beaks. The go for car mirrors, luggage racks, tyres, bumpers, wipers, badges, and a favourite is to turn spare tyre covers on 4WD's into ribbons.
I imagine they'd turn a tent into confetti with lightning speed. f you were camping and happened to wander off down to the creek for a few minutes, you could return to find a total disaster. It's just something they seem to like doing - wrecking inedible things! So.... boots?....probably.
I know! The boot tree is a totem to the Kea's offering thanks for not chewing up other things the hikers own. LOL