That's because of reuse, as kerosene burns slightly sooty, which can be cleaned but takes maintainance, whereas methane burns clean. You wouldn't use methane fo

That's because of reuse, as kerosene burns slightly sooty, which can be cleaned but takes maintainance, whereas methane burns clean. You wouldn't use methane for a single use engine unless you were buying off the shelf like Vulcan IMO, since its harder to use and doesn't perform better.