The launch pad is as much in development as the vehicle itself, so it's not at all clear what is "a proper launch pad" for this vehicle. And even once it's clear what it is, I've even seen some estimates that building one on that site may take years for reasons of local geology. Meanwhile they need to perform launch tests, so I'm not sure what else than MVP they're supposed to use. Clearly waiting a few years is not an option in a chicken-and-egg situation.