It’s due to climate change.
Majority of cars not use fossil fuels. Fossil fuels will eventually run out, release lots of C02 into the atmosphere as well as lots of other gases and dusts that are not good for the climate or for us breathing in.
Electric cars mean that all the fuel can be generated without any fossil fuels by changing electricity generation to using renewables such as hydro/wind/solar as well as nuclear power generation.
It’s been proven that co2 is causing the climate to change and that is down to co2 being release by humans. If the co2 levels drop then this will slow/stop and unnatural climate change. This has all been shown to be true and there is plenty of scientific evidence to back it up.