Aside from the Dwarven Axe and BS being Exotic weapons, and the Feat required, the Warhammer fills a few other roles. Worshippers of Onatar
use it as a favored weapon, it's used specifically in a few Feats/Trees, including Pick/Hammer training for Dwarves if they're working a CON blunt
build, for Destiny attacks like Anvil and Pulverizer, and some things have more resistance to Edged. Just as some examples I can remember.
Good question, and the strikethrough is nice to have with the DA/BS, but there's some instances I wouldn't bother.