How often do you use/need a 50 amp to 30 amp adapter?

A good 50A to 30A dog bone is a must have in your kit.

Do I have to use one often? No. Have I used one on occasion? Yes. Once or twice, it's been the difference of having electricity and not having electricity.

And what the others have mentioned about the 30A outlet being in much worse condition than the 50A outlet is also true. Many, many more people use 30A thab 50A, therefore the 30A outlet can be relatively worn, while the 50A outlet is nearly pristine.