I think it's because the environmental cost of making a brand new electric van has a higher environmental cost than just driving the van you already have until it dies. Basically the world would be better off if people stopped buying new vehicles tomorrow completely, and just drove whatever they have, no matter how polluting it is - it's still better on the planet than making a new one. Of course our economy doesn't work that way and it's a completely unworkable solution for now - so replacing ICE vans with electric ones is second best solution.