Best Reasons NOT to Gish

[AMFV]

I mean.. in a non DM environment like theorycraft. With a blankslate. There basically isn't ever a reason not to build Gishes. They're better Martials than actual Martials are. That's just 3.X in a nut shell though.

There are a couple situations that aren't being touched on here. If you never get enough Caster Levels to actually be doing anything, it might not be worth it. If I'm building a Hulking Hurler/Bloodstorm Blade character I have barely any levels to play with to add casting. That's initiator of course, so that wouldn't be exactly what OP was talking about but it's kind of that sort of situation. If I'm a Frenzied Berserker... I'm never going to be able to cast anyways so why would I spend build resources on something that I'm never going to be good at. And Frenzied Berserker is very strong, uniquely so actually.

But yeah generally the reason why you wouldn't gish is that often casting is really involved and you have to focus on it. Is a Fighter 5/Wizard one better than a Fighter 6 that just picked up the second Dungeon Crasher ACF level? Probably not. I mean sure you're weaker in many ways than a Wizard at that level, but basically if you're not going to be good at it then you're spending build resources on something you suck at, and that's kind of not very valuable.

Now there are ways to add casting/gishing later: Suel Arcanamach, Divine Crusader, Pious Templar, Ur-Priest even... and many others. That are generally very good and strong. But those are also mid to high level things and again if you're doing something like Eternal Blade or Bloodstorm Blade or Halfling Outrider... you're not going to have the levels to make any attempt at gishing good. From an optimization perspective that's when you don't bother with it.

Oh yeah, Ubermount! That's another one that doesn't want to Gish.

If the environment adds a DM they would have to modify something to make magic less desirable. But at that point, I don't see why they'd be playing 3.X. The caster god edition really.

This highlights one of the other reasons people might not want to Gish, because DMs are more likely to be more suspicious of gishy characters or casters and therefore are less likely to give you the benefit of the doubt when it comes to rulings. That's not always the case, but definitely that could be the case.

Past that.. personal preference? Maybe player got bored of casters lol?

This is the other reason why you wouldn't want to. Or just an extra challenge.