No, this is not the reason. EVs don't need big 12V batteries that can crank over a large engine, because they never have to do this. NB: Never, never jump start an ICE with your EV, you may damage the EV.
They are an achilles heel because:
- 12V batteries are designed for low normal electrical load with occasional massive cranking load: ie for ICE applications.
- EVs never need the cranking load but they can draw a fair bit especially in winter driving all the car's electronics, lighting and other systems directly off the battery.
- A 16V Lithium Ion battery is a better choice for an EV but manufacturers try to cut costs and use a traditional 12V.
- 12V battery quality has massively declined. The race to the bottom has led to low quality batteries that don't last.
- Many EVs have had bugs resulting in inadequate charging of the 12V battery from the main battery.