Protection

Unless the camper is not very valuable at all, I wouldn’t store mine outside in the off season without a cover.
And sun does as much or more damage than rain and snow.

While a roof is easier than a cover a cover does a good job.
There are places in this country I’d say a cover wouldn’t last long and could also scuff from flapping in the wind, but Indiana isnt one of those places unless there’s a tornaado or may be it’s stored on top of a big hill with no trees.
The 2 winters I’ve used a cover, the rv didn’t even need washed in the spring.

I used one for 13 years on our last rv and it looked like new when I traded it in. We get light to moderate wind here but rarely anything damaging.
FWIW, I keep our new rig under a carport and the old cover actually kept the rv cleaner over the winter.

It may or may not give as good protection, but, when the wind makes it flap it can abrade the outside of your RV.