The cynic in me winces when thinking of the mess all the banks and interested companies would make trying to get together and build a payment standard. Just look at the terrible mess of stuff like OFX.
Also it might not be necessary for the involved parties to get together. They could release different protocols. And then the lesser used will be forgotten (like gopher is forgotten today) and the more frequent used will survive (like http has survived).
Update: Why the downvotes?