David, the tape is more rigid (especially with a few layers) and the adhesion adds to the proprioception (sensory feedback) so that in theory, when you start to go over you feel the skin pulling in time for your muscles to catch you.
That’s a nice theory, and explains the benefit of stretchier tapes the tennis players wear on their arms, but sadly it’s still possible to go too far before you have time to react. Thankfully, the tape does help hold the swelling in if you have to keep on walking.
If you’re wearing low cut shoes or softer boots, the tape also prevents you getting too far over sideways on the ankle, before the ‘last straw’ incident that tears the ligament. That’s why you can’t sprain an ankle in a ski boot, it won’t allow too much sideways movement.
I use several braces for ‘light’ wear, like when recuperating from a new sprain and wearing business shoes, or walking the dog.
Sam, I’ve got legs like a lowland gorilla :), the problem is the muscles don’t always fire fast enough to catch me before the ligament tears. Even with poles, as David mentions. Ironically, it’s usually in an urban environment like a wet car park with a bit of oil slick, rather than out in the bush. Once you’ve had a complete tear of a ligament, it loses a lot of its proprioception, so it doesn’t tell you it’s being stretched until too late. Muscles have a lot more stretch in them, so they are slower to notice a twist.
The battle with splints and footwear is between too rigid which restricts rock-hopping, traversing etc, and not rigid enough! Maybe Elon or someone will invent a computerised boot that will automatically stiffen when you start to slip, like the Segway microchip maintains balance.