It's a good item, it's just not used because there are better alternatives. It doesn't give enough AD to satisfy people who would build hydra/bt/ie, it has no crit, no armor pen, no lifesteal, and its passive is nowhere near as good as that of BORK which has nearly identical stats. Just increasing the AD a bit would help a lot, but that would make its gold efficiency rediculously high. I don't think a boost to the movement speed would help very much at all, it would just be regarded as a better upgrade for boots. Increasing its attack speed wouldn't help too much either, as it has nothing which increased attack speed would work well with.
...speaking of which, I've had an idea. Give it an additional passive which is similar to wits end, except movement speed instead of magic resistance. Could then be made to build out of phage instead of pickaxe as well, which would be useful as it would give phage an additional build path rather than forcing the player down the triforce route.