I find this question funny. Personally I don't care what the merchant prefers - I use my credit cards on every possible occasion so as to get points and zero forex fees. Singapore is a major modern city so credit cards are accepted almost everywhere except as noted below.
Originally Posted by
SQTraveller
Cash is really only needed at hawker centres, small restaurants (those without AC) and small corner shops.
So yes, a small amount of cash is needed.
My experience as well. I was easily able to survive on USD $100 for a week, though I don't take too many taxis.