Gas mileage is the simple answer. Computer controlled engines is the second answer.
Believe it or not...stick shift cars get worse mileage. Because of this and the EPA mandates about MPG
the standard shift is no longer available in most cars.
You can still order it on certain models of cars, but you have to sign a waiver on the EPA papers. True.
Go check out a mustang or charger and ask about the stick shift option.
When I was in high school; and I bought a high performance car with a stick shift (4 speed) the cost of
insurance more than doubled. This was because I was under 18 also.
A friend had a 1969 Dodge Charger 426 hemi with a 4 speed. The papers on it said it had 390 HP. But in
reality it had almost 500 HP. It was de-rated in order for people to get insurance on it. He was paying over
$60 a month for insurance. And he was 19 years old. That's $720 a year for car insurance in 1969. When
the average job paid $2.25 an hour. That's about $360 a month.
Yeah, those 1960's cars were cool and all muscled up, but in reality, very few could afford them.
This is what the shifter looked like in my 1969 Oldsmobile 442-W30.