The vacuum advance helps provide the advance at low rpm when the mechanical advance does't operate. Being electronic or points doesn't have any bearing on the need for a vacuum advance, the vacuum advance allows for less base timing for easier starting. Performance distributors forgo the vacuum unit and rely on a quicker pickup of the mechanical advance, but this requires more base timing at idle/low rpm. The result is more power in the mid=high rpm range.
Modern engines use the computer to control the advance/timing.
