Well one advantage is that Singaporean employers can put on superfluous "must speak Mandarin" sentences in their job descriptions, which lets them hire Chinese people and avoid hiring Malay and Indians, all the while landing on the right side of anti-discrimination laws.
Hard to do that when lots of people speak Hokkien, Cantonese etc.
English is the official language used in formal context in Singapore, not Chinese, Indian or Malay. All the documents you’d sign with a company are in English.
Hard to do that when lots of people speak Hokkien, Cantonese etc.