The environmental stuff is actually just the icing on the cake - EVs have a number of advantages over internal combustion and the disadvantages keep getting smaller.

-awesome acceleration due to instant torque and no gearbox

-amazing handling due to low centre of gravity (heavy batteries at the bottom)

-quieter

-minimal servicing / repair costs due to much simpler drive train with fewer moving parts and no fluid

-more internal space (no crank shaft etc - especially in the back row this makes the middle seat so much more comfortable without a big bulge between your feet)

-more external space (e.g the Tesla S has a front trunk (frunk) where the engine normally is)

-safety factor - extra crumple space with the frunk and no engine to go into your legs in front on collision

-cheaper to run especially in high gas cost areas like Europe

-some areas have perks like using the HOV or bus lane

-convenience factor of 'filling up' at home

The environmental stuff is all goodness (and other responses have illustrated how this still holds even in coal dominated areas) but for many is not the driving factor.

Obviously EVs are not for everyone. My analogy is that they are like SSDs - better in every way except size (range) and cost, and therefore not viable for some...but that will rapidly change as the technology moves on.