What is the main reason why Lead-Acid batteries, despite being heavy and bulky, are still widely used as starter batteries in conventional internal combustion engine automobiles?

1. They have the highest energy density among all commercial batteries.
2. They can deliver very high surge currents required by the starter motor and are cost-effective.
3. They are completely environmentally friendly and easy to dispose of.
4. They do not require any maintenance or voltage regulation during their lifetime.