And on top of that, it was almost never worth it, since your DC is set by a flat 1d20+ability score modifier (the specific ability score depends on the chosen attack mode, none of them being Con), which means even against low-Will psionic characters (already there are not a lot), you generally had a lower-than-50% chance that the attack would affect them. And that's not even counting the fact that each attack mode affects a different ability score. If you wanted to lower the opponent's dexterity to 0, you would have to choose the same attack mode 3 to 4 turns in a row, allowing any psionic character to just choose the appropriate defense mode after the first round, making your attacks even more useless. That's easily the worst part of an already pretty ill-designed book, and it's a relief they completely cut it out from EPH.
To note: Characters with levels in psionic classes could also use attack/defense modes, but they had to pay power points for them. So the 3.0 psion, already one of the most MAD classes in all of d&d, had to expend daily resources to be allowed to be useless. Great. All-around great.