People confuse stupidity with personality. None of the LIs are stupid. They're all, in one form or another, vulnerable, that's what makes the corruption/dark routes work so well. If they were all founts of independence and self-confidence and knew what they wanted and what was good for them, we wouldn't really have a game here.
Characters like Nicki, Mason, Risa, and Brit were all abused or neglected in their youth. Abuse and neglect at a young age develops personality issues. People with personality issues don't assert themselves in healthy ways. That's why a lot of them hover around people that abuse or devalue them. It's a coping mechanism that was ingrained in them in their formative years. When someone treats them like shit, their instinct is to blame themselves instead of the abuser, because that's what they did as children; that's what children do, they internalize their environment.
Even a character like Ashe, though, who seems to have grown up in a healthy family, had an early tramautic event in her life that affected her self-perception; the car accident with Wren. So, aside from the typical things that would control her reaction to findom/dark Guy, I think there could also be some guilt and self-blame there.
At least, that's how I interpret all of it. Neon can have a different idea of why his characters behave the way they do, and there's probably more complexity involved, I'm simplifying it a little.
I think you can also view some of the men in the game through that lens, too. Men tend to react with more anti-social behavior and violence when they're subjected to early neglect/abuse. Plus, the LIs have to be written to be likable or the game doesn't work as well, whereas the guys have more room to be assholes. Characters like Isabella and Tessa are the hateful bitches of the game, maybe representing the much more toxic personality that can develop from neglect/abuse/trauma, but that's also why they're not main LIs.
