because you're running two pumps off the same power feed instead of one. If you want to use a 30amp relay, you're gonna wanna use a power feed and relay for each pump, but they arent wired from DCR to even be able to do that.
I think the amp draw of one pump is around 20amps, so two pumps would be 40amps....even if the relay did work, why would you want to run the relay at the edge of what it's designed for when it will likely fail and burn out and let you sitting somewhere???
If you got the money to install a twin 044 setup, then having a good, decent electrial system for it shouldn't even become a question.