Sometimes one of the few guaranteed ways to deal damage to a high AC fighter is with spells with reflex saves (even with a save they take some damage, and lots of times they don't save) High level fighters have a tendency to laugh of these spells anyway because they have sooooo many hit points. That being said there are two ways of looking at it:
1- Reflex spells aren've very effective against fighters anyway so making them less effective is no big deal
2- Reflex spells are one of the few things which can cause damage to a fighter and anything to change that would really upset game balance.
I'm inclined to go with the latter. Rationally it may seem like a good idea, but game mechanic wise it's a bad, bad idea.