You wanting to reserve space for the big numbers of the large, personal things called cars, both in terms of parking space and having to cover half of the city in asphalt, with the subsequent growth in distances between points (because of lower density), makes the city less accessible by anything other than a car and deprives others of their ability to just walk or bike their way around, is less aesthetic and causes air pollution... and besides, you couldn't just rebuild the central Helsinki area (which is quite fine as it is) for cars for everyone (in particular building the underground parking caves is hideously expensive).
Outside of the city, you can go driving all you want, there's a lot of road in the woods in Finland. Personally I live in one of Helsinki's exurb towns which is your typical place of single-family houses with big yards... I guess you'd like it here. I have the pleasure of driving to work every morning and I'm not all that certain it's such a great sign of my freedom -- I just get to operate the controls in a certain fixed sequence twice a day. The place also has this distinct sleepy sense of nothing ever happening, so I find myself heading to the city whenever I want to actually get some action.