However, in contrast to the D&D inspired popular view, warhammers and maces were specialized anti-armor weapons, not an alternative general sidearm. If you were going to carry a end-weighted weapon, it might as well be an axe. You get the same sort of momentum advantage, plus the benefit of an edge. The popular view of battle axes is also waaaay out of line with reality.

The other benefit of an axe is that it's very good as a battle utility - pulling the opponent's shield out of the way, for example.