Have they? It seems that when rubber meets the road, so to speak, it is not a simple one-to-one replacement for gas or diesel vehicles. The day-to-day ownership is more complicated, planning your itinerary and day around sparse public charging and owning property to have at-home charging. Also, the long-term ownership, having low resale value due to the high repair costs of the electric drivetrain and low overall repairability, makes ownership a poor proposition for most average people.
Electric cars have been on the market for over a decade. Show me one that someone has kept past 200,000 miles. Meanwhile, you can find Toyotas and Hondas well past that benchmark all day on Marketplace.