Well for one thing it's the best Electric-type that can be acquired relatively early in the game (I tried Joltik and Blitzle; the former was too fragile later in the game and the latter didn't have a very versatile moveset.).

For another thing, it's an Electric-type with a Ground resistance, which is always great. Hell, it resists everything except Rock and Ice attacks, which are few and far between.

And lastly, I almost always have a team of fully-evolved behemoths in my Pokemon games. Sure, all-out brawls between two huge monsters is awesome, but you know what's more awesome?

Cheren's 10-foot Serperior and Bianca's 300-pound Emboar. Being taken down in one shot. By something smaller than Pikachu.