Earlier quoted context omitted.
Selling a service automatically opts you in to all kinds of consumer protections, either legally or de facto through the dispute mechanism of the payment methods your customers use. Just ignoring customer complaints and selling the service "as-is" is usually not an option.
Why is it not an option when it already exists in many places (all these protections fail all the time)? Your first sentence doesn't imply high/expensive level of customer service Besides, even now they're not ignoring all the complaints, the do fix bugs? Maybe to be more specific, how much did it cost WhatsApp when they had $1 price and a tiny team? How does it compare to the cost of SMS?
FB acquired them next year and if my memory is correct there were 19 in the team then.