The City of LA for one, requires any portable generator be grounded. When we are out doing special events, etc. its either staked or on a water pipe, etc. It's a safety thing only and has nothing to do with conditioning the output. What we do has a LOT of lighting ballasts and remote light heads on the ground or that may also be attached to scaffolding that itself is grounded and I have been knocked on my can more than once when someone neglects to ground the genset and someone screws up the wiring (way too common). BUT, RV service is completely different. Do I do it with my Honda generator with a 100% plastic and isolated case? NO. There is no path to ground anywhere in the RV, so why create one?