The old saying is...

Don’t put all your eggs in one basket”

Since EV’s from an automaker are using one cell design in their battery packs,
they can end up like GM did with the LG made lithium cells that were defective and started fires
and could end up with no new vehicles to sell.

Having new IC engined vehicles to sell is a type of survival insurance,
as is further building up the sale of second hand IC engined vehicles as we witnessed in the “chip shortage”.