There was another incident in Florida, I think last September, where a driver ran a red light and struck and killed two pedestrians, sisters age 5 and 2. The driver has since turned herself in to face vehicular manslaughter charges. This may turn out that it might not be vehicular manslaughter, simply because under Florida law running a red light is not considered reckless driving and in order to be vehicular manslaughter reckless driving has to be proven.

The thing I don't understand at all is why isn't there an automatic, on the spot, vehicular manslaughter charge for cases like these and any time a driver does something illegal that kills somebody.

The vast majority of motor vehicle incidents are not accidents at all. They happen because one or more drivers were negligent.