You've lumped together companies that do very different things. I would just google "payment card network" and you can spend days going down rabbit holes to understand how complex the system is. And yes it is all totally necessary: https://www.spreedly.com/blog/card-processing-network

"Visa, Mastercard, Discover, and AmEx also form the PCI Security Standards Council (SSC) alongside Japan’s JCB International. The PCI SSC acts as an authority in the payments industry, regulating and enforcing the PCI Data Security Standard (DSS) to protect cardholder information. The rules set by this consortium are not guidelines, but the ground-rules participants must abide by in order to participate in card-payments."