The big thing is cost (which will go down over time with improvements in battery technology), but you also have to figure out charging as well.
The Tesla Model S has a 85 kWh battery bank. The average price for power is 10 cents per kWH in Maryland (even solar). So that's $1.20 to "fill up the tank" in raw power alone. Plus, it's not a quick fill-up.
That's not economical for a gas station. A rest stop or a restaurant (even a Royal Farm)? Drop in the bucket. So you'll have to dot rest stops with charging stations, seating and a lunch counter all over the place.... instead of gas stations. Well, that's a shift in thinking. And something the gas/oil companies aren't ready for.