It's the chicken and the egg scenario. Take businesses coming in to the city. They'll hardly be concerned about infrastructure and the council will hardly stop businesses coming in because of it, either.
There are also cities that have spent fortunes on infrastructure, been way too ambitious and found they'd wasted money on projects that either never started or were barely used and cancelled. Like many things, hindsight is a wonderful thing. Having said that, I do agree that Cardiff Council has dragged its feet on this for way too long. They won't be the first, they won't be the last.