Most people don't care about performance cars. They associate these cars with a mid-life crisis or a someone who is compensating for something. Most people look at these cars as impractical, expensive, hard to drive, pointless, and cause more trouble than they are worth. Yes people will admit they look cool, but they don't see what us car guys see. They don't see something that is worth the money, time, and effort. But there is a reason normal people should care about performance cars. If it weren't for the McLarens, Porsches, BMWs, Corvettes, and all other sports cars, super cars, and hyper cars, then normal cars would not be anywhere near as advanced as they are now.
Lets take a look back to the '60s. A period of 15 second 0-60 times, 240 foot 60-0 stopping distances, drum brakes, squishy suspension, and bias ply tires. Lets take a look at a piece of technology that is easy to understand, brakes. The majority of cars in that period had drum brakes and would stop extremely slowly. So slowly that a tortoise could probably cross the road before you came to a dead stop from 60 mph. The performance cars of the day did not come with drum brakes. Disc brakes were taking over the world of sports cars and racing. As a result, sports cars were able to stop far quicker than normal cars. Disc brakes slowly became cheaper to produce and more common on normal cars into the '70s.
As time and technology progressed the more disc brakes advanced. The newest technology on performance cars are carbon ceramic brakes, which are starting to get cheaper and more common. They might not be on normal cars yet, but they are far more common on sports cars now. So why does this matter? Why do the brakes on sports cars and super cars really matter? Well imagine a kid walks into the street, or a car pulls out last minute. If you don't have good brakes that situation will end in possibly an ambulance and the police at the scene. But with modern vented brakes and ceramic or semi-metallic pads, the situation won't end that way.
Even if a manufacturer doesn't have a performance car to offer, chances are they will quite easily be able to get a hold of the latest technology once it is cheaper and offer it in their cars. This is done through shared resources and technology through being in the same family as other manufacturers. VW Group has Porsche and Audi (not counting Lamborghini since they are designed by Audi), Fiat-Chrysler has Ferrari and SRT, GM has the Corvette name, I can keep going on. The point is that the technology from the performance cars is shared throughout the other companies as the tech becomes cheaper to produce. But without performance cars needing this technology, it does not make as much sense for manufacturers to put so much money into development. So development of better technology would happen a lot slower if at all.
This goes for all parts of a car, the chassis, suspension, tires, brakes, power, transmissions. Chassis rigidity is extremely good in the average modern car, about as good as a twenty year old sports car. Active suspension came from sports cars and super cars and can now be found in many normal cars. Road tires improve every year because of testing and pushing the limit of hyper cars and super cars. Brakes improve. Horsepower outputs have vastly increased, A new BMW 330i has the same power figures as an E36 M3.
To really drive the point home lets look at the former USSR, a country that almost completely lacked sports cars. Now look at the most common car they had, the Lada, a rebadged Fiat basically. The car didn't change over its entire production run, which was from 1970 until the fall of the Soviet Union. In that time Volkswagen progressed from the humble Beetle to the third generation Jetta. Audi went from building rebadged VW Foxes to building turbocharged awd sedans. The first naturally aspirated production engine to put out 100 hp per liter was put into production. Tires went from bias ply to radial. Suspension went from cars being like boats to actually cornering, in comparison, pretty flat. Yet the Lada remained pretty unchanged. All this development is thanks to cars like the Countach, F40, 959, Corvette, Quattro, 911, M3, M1, and many other excellent sports cars and super cars.