Originally Posted by
Pex
It's the spells themselves. Depending on the spell even if the target fails the save you don't get what you wanted the spell to do. You only get a minor inconvenience. The target has to critically fail to get the effect you wanted. Roll a 1 or (10 or more) below the target number. Therefore the spell is highly unreliable. Buff spells don't have this problem, which is why they're more valued.
It is a limitation that nerfs spellcasters. It's not even a "punishment" that I soap box against. I'm not a fan of it either. Complain all you want spellcasters are too powerful. They're still entitled to have the spells they do get to work.