D&D is a very watered down, simplified and therefore highly inaccurate system to represent reality. The pike was an amazing weapon both in armies and in single combat. The notion that it wasn't used in small scale conflicts isn't true. It was even a favoured weapon in duels. Reach is, basically, almost always a significant benefit. You would be crazy to use a rapier against a pike, for instance, unless you were really good with rapier and buckler and your opponent was pretty crap at the pike. And in formation, that reach, especially when forming two lines, was phenomenally effective against armies who didn't have their own pikemen.
But, that's not D&D. Honestly, they should've just called it a spear or, at worst, a long spear.