cab-less or just plain luck-less?

Ever tried to get a cab but none avaliable? It is either you have no luck or there was no cab then. I don't take a cab but then yesterday I had to hail one for work related, there are no cabs avaliable. They are all hired or busy. To make matter worse, I can only go for comfort-delgro cabs. I had spent 45mins that I decide to go back to my company main lobby when a cab pulls in with an alighting passenger. So what could the problem be? Either that the cab business is doing well that most of them aren't at work yet or they are all at other places. When you don't need a cab they are all around you but when you need one none avaliable. Maybe it is just plain no luck...