Even in the past, that was a bad idea, just not as sensitive as today's electronics. When ever possible, you should always bring a battery back to life using a battery charger. An alternator is designed to maintain battery voltage. Charging a battery from dead using an alternator requires a huge amount of amperage. Large draws like that can greatly reduce the life of the components in an alternator. Yes I know it is done all the time, but that does not mean it is the best way to handle the issue.

James