Intriguing Observation about Singapore

I have visited Singapore many times but never though about this until pointed out today by Dilip and Charu Kokate that one never sees a laborer (whether from India, Malayasia, or any other country) on Orchard Road or any other major pla ces of tourist attraction. There are significant number of these workers here, but I have never seen any of them at any place except on Sunday afternoon in Little India. Why does this happen? This is very intriguing. I can not think of a reason for this to happen or how could the system control this?