It is mainly to reduce fuel consumption.
When cars travel forward, they have to cut through the air in front of them. This causes air resistance on the car, which slows it down. The more streamlined a car's design, the better the air flows over the top of (or underneath) a vehicle, which reduces the amount of air resistance acting on the vehicle.
This means that cars can be more fuel efficient. They do not need to use as much energy overcoming air resistance.
* Although this is not as critical for ordinary vehicles as it is for race cars and aircraft, increased air resistance results in the use of more fuel to travel the same distance, and even more at higher speeds. So most newer cars are lower and narrower, and shaped to pass through the air efficiently. Reducing fuel consumption ("improving mileage") also means that smaller fuel tanks are required to travel the same distances, which further improves mileage by reducing vehicle weight.
The most common features in modern cars that help to reduce air friction is the streamlined design of the bumpers and spoilers. The streamlined shape of fast cars also helps to reduce drag.
It's a marketing image that symbolises speed. The jaguar is a fast animal, with a streamlined body. The car of the same name is designed to be streamlined, and is a fast vehicle.
Cars with good aerodynamics.
Their shape and aerodynamic efficiency makes them streamlined.
aircrafts and fast cars are streamlined so that the air flows over them more easily
They have a streamlined bonnet so that the air will be pushed over the car.
Advantage- their sleek, sexy, cheap, powerfull, fuel efiecent, well designed exterior diaadvantage- interior is cheap, bulky, all cars except golf gti and cc are ugly, copy other cars
Helps improve fuel mileage.
the way they were desinged by the builders
race cars are streamlined so that they can try to be as quick as possible and also so that they can acheive the highest speeds that they can. i mean they are streamlined because they want to be quick and overall they wont to win the race :)