One of the big issues government IT faces is cost of providing different channels for business with different IT capabilities.
For the same program, a government needs to provide say a web based portal (or even an email solution) for a very small businesses, a web-service for a medium size businesses, a B2B solution for a large businesses , and so on. Large amount of program money is spent these IT structures/channels which could otherwise be used for actual program.
4-Corner model, which was first used for Superfund industry (Superstream) and now for procurement industry ( E-invoicing) helps Govt to reduce many channels to a single channel while delegating other channels to commercial gateways and therefore also helping create a new industry of commercial gateways.