Because of shallow movepool. Since the most important electric attacks, Volt Switch, Thunderbolt, Thunder Cage, etc. are special, most people run choice specs. Apart from these, what different special attacks it has? Ancient Power, Hyper beam, Round, Snore, and Swift. All these moves are useless, except uh... maybe Ancient Power. That's why they use 3 moves of same type. The new Regis have bad movepool, urging them to use moves of same type.