I'm sorry, but what we know about cognitive science is that people quite often do 1) act unreasonably, and 2) forgo the choice which decision analysis would indicate that they should take. That's a rabbit hole that we probably should avoid, but if we do, are you prepared to roll up your sleeves on this?
"Believing men would act in their own interest was not cynicism, it turned out, but sheerest optimism; in reality men do not meet so high a standard." A fair point. And of course, the freedom of choice means freedom to make the wrong choice.
I'd rather take this back to the original point of this thread, which (I think) is about making a character that doesn't fulfill its role in the group. If you join some players at level 10, and you present your level 10 Fighter/Champion with Strength/Dex/Int 14, are the other PCs going to welcome you to their party? Or are they going to question your competence, given your lack of physical ability relative to what they expect of their peers? Are they going to trust you to do your job, knowing fully that a failure on your part could mean that they all die? That's the in-character question which needs to be answered.
The out-of-character question, which some other people might care about, is will the other
players be happy to see you bring this character to their table? Do they
care if this character is not as good at its role, knowing that you could get them all killed by your decision to play a character that is
intentionally less powerful than they expect it to be? Would
they be happy to see you choose +1 to Int/Wis/Cha checks, over +3 to hit and damage?
There's a difference between a character that is fully optimized with every point in the right place and every decision analyzed thoroughly, and baseline expected competency. Bothering to max out your main stat is where I (personally) draw the line for baseline competency; if you don't even do that, or do something at least as obviously useful, then it's like you're not even
trying. It's like you don't
care at all, and that's not going to go over so well at some tables.
I'd be interested in hearing where other people draw that line, but I'm not sure if this is the right thread for that. Or it might be; it's been kind of all over the place.