At least in cities and during the day, good public transport is faster than cars at any distance. In London or Paris (and even New York), you'll see hedge fund managers on the subway.
Even so, even in say, Paris inside the ring, it's typically faster to take a taxi than the Metro. Go on Google maps and pick some random routes and see for yourself.
As soon as you go to a smaller city or travel outside the densest part of the city, the car becomes dramatically faster.
My observation is that hedge fund managers do not typically take the subway. They have chauffeured cars so that they can make productive use of their time while driving. In the rare instance that transit is faster, being able to simply sit down and take calls, do email, etc is very valuable and is not practical on most forms of transit. Certainly confidential calls are a no-go, and laptops are not practical except on some commuter rail. Furthermore, on most transit trips, the time is broken up. At minimum you have walking time, then waiting time, then moving time, then more walking time. With transfers it's broken up even more. You'd be lucky to have 1/3 of the time sitting in a seat where you could peck out emails on a smartphone.