We do not cover ours and it does not seem to hurt.
Our van has steel wheels for summer and winter tires, so has factory wheel covers. But in winter, there is more risk to losing them and also they are more prone to damage from sand/rocks, so we do not bother putting them on.
The Pathy has alloys for summer and steel for winter and I do not bother with them either. I think it is more a cosmetic issue.
But if I am wrong, I am sure someone will let me know
