It's not a matter of needing each other. As long as there's a positive NPV on working together, they'll do it. They each might say, "We benefit X, but there's

It's not a matter of needing each other. As long as there's a positive NPV on working together, they'll do it. They each might say, "We benefit X, but there's a risk that costs Y." As long as X is greater than Y, they'll work together. They don't have to, but as long as they're the best partners for a given transaction, why not?