Because at the end of the day the Ferrari (or Porsche or Lamborghini) design is not a very comfortable or practical design for day to day use. The (two) people I know who own Porsche sports cars also own a second car.
People who have sports cars tend to have a second (or third or fourth) car because they have the funds available to afford being able to have other options available. Some Porsche sports cars are tremendous daily drivers -- a 911 Turbo is simultaneously a race car, a Toyota Camry, a snowmobile and a Bentley.
Sold Porsches in a former life. Third car was most typical, with it only being used for pleasure and special occasions. 911s were usually used most often as daily drivers, as opposed to the mid-engine cars, even though the MR layout cars have more cargo space (10 or 15 cubic feet). I'm a very rare breed, considering I live in New England and mine doesn't even have a proper roof (manual "procedure" to remove/install instead of a single button, and is always driven top down, regardless of weather).
Last year Porsche made 230K cars. In their history Ferrari have made 130K. Lamborghini made 3.2K cars last year.
https://en.wikipedia.org/wiki/Porsche#Production_and_sales
https://en.wikipedia.org/wiki/Ferrari#Road_cars
https://en.wikipedia.org/wiki/Lamborghini#Products
Porsche are pretty much a normal factory car. They have low volumes and go fast. But that is pretty much where they stand. Ferraris and Laborghinis are far closer to being hand made.
Factory made cars are more reliable than hand built cars. People who have owned these cars have told me using a Porsche for a day to day car is doable. A Ferrari or Lamborghini probably isn't reliable enough.
Many people on the street owned Porsches, Ferraris, and there were two Lamborghinis, most were used daily. But, I think there was a restriction of one car per household parked on the street, and most would only have been driving a very short distance through central London -- usually at about 5-6am, before there was much traffic.
BMWs, Mercedes and Lexus cars were more common than the sports cars, and Porsche cars more common than Ferraris and Lamborghinis.
[1] https://www.google.dk/maps/@51.488953,-0.1788157,3a,75y,230.... (take left turns, I think there are five Porsches, and something I don't recognize. But this is probably the weekend, when most of the rich people were away, and normal people "borrowed" the parking spaces. A Porsche shop is 2 minutes walk away, the Lamborghini shop about 5 minutes.)
There's a retired F1 driver who uses a Ferrari Mondial as a daily driver. That's the opposite of the concept in the op question: A Ferrari that looks somewhat more conventional, yet is a true Ferrari under the bodywork. (It was also quite a bit more reliable than its peers.)