(1) It probably disappeared because of the Singapore Government's clampdown on drugs in the early 70s, which was at that time associated with rock music and western depravity. It was called, "Yellow Culture."
(2) According to some 60s Singapore artistes that Andy has interviewed, it also disappeared because of the extreme record-piracy then. Much money was lost because pirated records were being sold on the open market.
(3) Henry Suriya, a 60s crooner and elder brother to Naomi and Robert (The Boys), remembers that when his fans pushed him his EP records to be signed, he noticed that they were mostly pirated copies.
He smiled and signed them all but it was an unpleasant experience to see only bootleg versions of his own records. Imagine the amount of revenue/royalties the local artistes would have lost. Ironically, the pirates who made copies of these records benefited.
(4) Unpleasant conflicts in some of the 60s nightspots led to physical abuse and fights. There were also unruly elements at the nightclubs and dance venues. As these incidents increased, these places were closed down.