No parking sign (137/365)

I chanced upon this on the way back home today. I have seen no parking signs before, and the threat of towing away the car. but now they give the number to call if you found your car being towed away.

reminds me, over the weekends, i made my first call to LTA to complain of a illegally parked car. when you want to make a complaint, you have to give your name as well! i was quite surprised at first. but anyway, LTA has all the names and numbers of registered car plate owners. So when we make a complaint, they will just call the owner and ask him to move his car. How come some places can allow people to park illegally and just call to remind them. whereas places like this, have to be towed away? what are the regulations?