In case of ransomware, criminals are exploiting the very difficulty of victims to coordinate their actions. They depend on you paying instead of solving it yourself, educating others, or even simply calling the police. In other words, they profit directly off people's short-term, selfish thinking. The advice of defaulting to not paying is sound because if enough people follow it, the whole ransom stops being viable, which makes ransomware attacks stop coming.

The same, by the way, is the tried and true way of dealing with regular, meatspace, "I kidnapped your daughter" ransom cases.

It isn't going to affect them much. But as anybody who runs a business knows, the difference between loss and profit generally hinges on a number of sensitive factors. Note, for example, that drug dealing pays so poorly that many drug dealers live with their moms:

http://articles.latimes.com/2005/apr/24/opinion/oe-dubner24

Refusing to pay on your own doesn't help other people much, but it still helps.