Because if the fuel tank breaks you can just weld pretty much any replacement on and it'll work, you could even use a bucket on the back of your pick-up trunk &

Because if the fuel tank breaks you can just weld pretty much any replacement on and it'll work, you could even use a bucket on the back of your pick-up trunk & a hose as a temporary replacement. That's not the case with electric cars and their batteries. They're deeply integrated with the rest of the powertrain.