back in the mid 70's
most cars had mechanical pumps feeding the carbs, which delivered the fuel with low pressure.
Fuel injectors need higher pressure, thus the need for electronic fuel pumps.
Although I may well be wrong, I'm buying into the that the fuel it's self, adds pressure, helping the fuel pump push the gas to the injectors. The ancient Romans were able to push water up hill by the pressure created by volume in tanks. They also manipulated the flow but first they need the pressure.