To buy a HDB means to own a HDB? I don't think buy is the correct word to describe it. Rent would be a more appropriate word. One don't own anything be it condo, HDB or landed in Singapore. One is merely renting the premises which encompasses the liability of a REAL OWNER (which obviously is not you) in the form of property taxes, conservancy fee, maintanence, etc.... how else can you make a leasee pay for all these fees and still take care of the rental accommodation for you?
Do you pay for car servicing, road tax, insurance, tire change, oil change, all other car maintenance, etc.. when you rent a car from a car rental company?
How would you behaviour be if you own the car instead? Will you take good care of your own car?
That leads to another question.... does Singapore has a high home ownership? I think based on my analogy, you can decide for yourself.