How much effort and money really goes into making vehicles controllable? Its a staple in every modern-day open world game so it should hardly be too much to ask if you want your game to play in this space. Especially now that SP decided to situate the game in a real city, the dissonance here only becomes more pronounced.
As for how much use they would get, that all depends on how well devs design their game. A little imagination goes a long way. Personally, I think it would be pretty cool if Delsin could hop on a motorcycle, use his smoke power to dematerialize with the bike to the top of a building and then start hopping from rooftop to rooftop across the city, a little like Ghost Rider. That'd certainly make for some cool gifs like the ones you posted earlier