Hi Kesa,
Sorry for the brief reply before.
There is a perception that electric drive is best suited to city driving, where the constant start-stop traffic allows electric cars to express their full advantage through the use of regenerative braking. Electric cars have the greatest efficiency gains over conventional cars in city traffic and people tend to think that small cars are best in the city.
Another perspective is that electric drivetrains enable you to make a vehicle more compact.
However, i completely agree with you that minivans are a great opportunity. They usually would not need a long range if used for school runs etc. (and they don't need 760hp like a Model X - what am i saying?!)
Another reason that the focus has been on small electric cars is that the inverter/motor control electronics for higher power drivetrains is still developing. Heavy trucks are a perfect candidate for electric drive (imagine regenerative braking recharging your batteries while your 40T truck rolls smoothly down a steep hill), but the power required is enormous. I think Tesla are working on this.