David Weaver
...I hadn't really thought about it with gouges, but two things come to mind as far as removing material where end grain is present - unlike mortising, they don't have to push grain off of the sides of a cut. They sever it instead of wedging it off - in all parts of the cut.

And, a good part of the severing cut is not across the to of the grain, but rather slicing through the grain at some diagonal. That's also better.

Knowing why isn't that important, though. I've thought about the diagonal bit before, but not the fact that the wedging requires breaking side grain off.