The difference is that power companies aren't liable when their services are used to distribute child porn. This is the problem with cancel culture. Without any external pressure, there is no reason for Visa and Mastercard to care about regulating porn at all because that's creating an unnecessary cost center for the sole purpose of rejecting revenue sources. In these sort of cases, a group of busybodies, which can be anyone from politicians to keyboard warriors, want to cancel something, but are too uncreative and lazy create a set of standards and moderate the content themselves. Instead, they choose to pressure those in their reach to act, which in this case is Visa and Mastercard. This way, Visa and Mastercard receive all the backlash to the rules instead of themselves. Don't blame the companies for responding to market incentives. Blame the people who are creating them. This applies basically for all forms of internet censorship (e.g. Youtube).