Isn’t it plausible that a clever species such as our own might need less pain, precisely because we are capable of intelligently working out what is good for us, and what damaging events we should avoid? Isn’t it plausible that an unintelligent species might need a massive wallop of pain, to drive home a lesson that we can learn with less powerful inducement?
There is an alternative to pain as an incentive mechanism: dispensing with incentives altogether and just programming the organism with instructions to follow. And if the organism doesn’t already have “feelings” as a part of its infrastructure then the instructions are the only alternative. The big question for theories of pain and pleasure as an incentive mechanism is why mother nature as Principal bothers with incentives at all.