No-contact (accompanied by a solid, mutually-agreed upon transparency plan) covers TWO things:
1) It protects the betrayed spouse against the spouse who is unwilling and/or deceitful; and
2) It protects the betrayed spouse (and helps the wayward spouse) when the wayward spouse is WILLING, but UNABLE (weak, too nice to end it with OP, etc., etc.).
Again, just think of the alcoholic, or the person with the gambling addiction for your analogy. Yeah, some of them are just morally bad people who have zero intention of stopping what they are doing, but there are also plenty who truly WANT to stop . . . but can't.
I see so many betrayed spouses on these forums say something along the lines of "I believe her," or "He's sincere -- I can tell, I KNOW him . . . " etc. Well, just because they WANNA, doesn't mean they CAN.
It's not a guarantee -- nothing is. But a unequivocal no-contact letter sent, accompanied by a STRONG transparency plan, plus MCing with a MC specifically trained to deal with infidelity . . .equals your BEST chance of success!