For fighters "moving over just a couple of steps" can mean the difference being able to do something that turn versus nothing.
Um, a big part of the reason why Earthquake no longer has friendly fire is because it was literally garbage when it did have friendly fire. Horrific Scream is kinda mediocre as it is even without friendly fire.
You are quite right that this doesn't really affect spellcasters because most spells already have FF on already. Which means that everyone else gets a nerf to effectiveness.
I'm just saying that it might seem to be only a small change, but small changes can have big consequences, so be cautious.
