Subject title says it all.
I find myself regularly running out of piety on my Paladin. I get indirectly punished just for using my class mechanics and at points even ran out of piety. In such cases I'd be locked out of getting a god save or using -prayer.
Non-divine classes that don't have anything to spend piety on don't run into this issue.
Divine classes shouldn't be worse at divine stuff than non-divine classes.