Why would anyone build Pikes...

[llewellyn]

yes the correct deployment and use of pikes, if used correctly in tandem with either archers or muskets and some heavy cav your armies take minimal losses while destroying the other army near to completion. if you have question there was a thread about the best pike unit and correct use of said units
Pikemen vs. Swordsmen - an analysis there is one it should help

[mbrasher1]

Yes, but halberds also has long spears and all of the benefit of pikes PLUS they have AP and are available earlier.

So why pikes if you have halberds?