The covers are going to rub on a fully enclosed shock too, you just don't see it. The rubbing isn't going to be significant enough to weaken the springs or cause stress cracks in the shocks' lifetime, the hydraulic valving and seals will be worn out inside long before that ever happened, or your grandchildren will be riding it. You might eventually wear through the chrome, but again, that isn't weakening the spring or causing stress cracks. Don't sweat such minutia 'cause if your spring breaks it was a bad spring or you're way too fat. It just bloody isn't going to happen from rubbing the cover.
I like the open spring look better on most bikes anyway.