I carry the same adapter "just in case". I actually needed it this past summer when we stayed near Graceland - the RV park had all of the 30 amp outlets installed upside down near the edge of the box, where the cord got in the way if you tried to plug in. We could have survived on the 20 amp outlet but this way we didn't need to turn off the A/C to run the microwave.
The same goes for a 30-amp RV extension cord. You don't often need them in the US (I've only used mine 2-3 times), but I've read of Canadian parks which have the power pole 75+ feet minimum from the parking pad.
One caveat on using the 50-to-30 adapter. If you can, buy one that includes a 30 amp circuit breaker right on the adapter. Not many have them. You are really tapping into a 120 volt 50 amp circuit which means you could theoretically overload the power cord between the power pole and the pod's converter. Having the 30 amp breaker on the adapter will prevent that.