Originally Posted by TexSkier
I would assume it's there to keep gates, twigs, branches, etc from getting caught under the buckle while moving at speed. The bump deflects whatever hits the boot so it goes over the top of the buckle instead of underneath, where it could get stuck or rip the buckle off.
This. It's a lot easier to see its utility on a boot that has seen some use. Fortunately, I have a pair of Lange RS boots right here that have three seasons of fairly heavy usage on them. Here's a shot of the toe of my left boot:
Here, it's easy to see all of the scratches along the side of the boot, each one of which represents me scraping my boot against something as I passed it. Mostly trees and rocks. You can also see the damage along the leading edge of the front buckle, and how that bump prevents the underside of the buckle from being exposed. It's also worth noting that my second buckle was, in fact, ripped off while I was skiing. I skied a tree run a couple seasons ago, went down to unbuckle my boots before I got on the lift, and the buckle was gone. I always ski with those buckles "up", meaning the bale is in the teeth of the buckle, but it's not cammed down, which both made the buckle vulnerable to being ripped off, and also made it so I didn't care that it was gone.