You are missing WHY it's only used "1/4 of the time".
The whole idea behind a hybrid is to use the electric motor in two cases:
Obviously, the engine is shut off in the first case. But, most people don't realize that small bursts of acceleration occur all the time in normal city driving, and the electric motor can be engaged while the gasoline engine remains running at a constant (and efficient) speed.
So, where does the charging torque come from? There are three sources:
There is certainly a weight penalty imposed by the motor/generator and battery. But, the efficiency gained by the above more than makes up for it.
At current gasoline prices, it's difficult to make up the additional cost of a hybrid over the lifetime of the car. But, that hasn't always been true. And, it's difficult to predict how long it will remain true.
1/4 is 1/4.
Why doesn’t matter.
It’s a monumental scam.