In the end, does it really matter what somebody is charged with if the punishment fits the circumstances of the case?
To be convicted of murder, the mental element to prove is 'malice aforethought' but until about 50 years ago (?) that was 'express or implied'. Implied malice meant that if you killed somebody, even accidentally, whilst committing a serious crime (known in those days as a felony) it was murder. And, theoretically, the rope. Fair enough, I hear many cry, but it led to a lot of 'perverse' acquittals by juries who did not feel that somebody should be hanged in a particular case.
Since a mandatory life sentence has been the punishment for murder, all manner of reasons have been accepted to reduce that charge to manslaughter. There has been a tug-o-war going on for some time between the judiciary who want discretionary sentencing for murder and politicians who feel that they must act tough.
I know that may people on here feel that sentences for drivers who kill are inadequate and they may have a point, but I cannot see how calling it manslaughter - for which there is normally no mandatory life sentence - would make much difference.