in Australia, ALL busy areas has parking officers onsite. walking up and down or drive street by street to check the time to PRINT out tickets. Yes, they all got a small handheld printer since they have to issue so many tickets per day.
the reason is simple, if one can park for the whole day for free, then other customers can't park to shops. also this means more money for the government.
But i guess HK is different, car is not an necessary item. this is like in Australia public transport is not an essential thing. one train or bus per hour. So people or the government usually don't care how they would run. therefore just unlucky for those drivers who got tickets.