I think they try to dismiss it to maintain a status quo. Somewhere deep inside, subconsciously, they know the truth, but the inability to stick to nofap make them insecure, and every time somebody says nofap works it's like a trigger for them, they immediately start feeling a "need" to prove that person nofap is bullshit to make yourself feel better. Also they tend to tell themselves good stories, like: "doctors say you should fap at least once a week or you'll get prostate cancer", "it reduces stress", "it helps you to sleep better" and so on. Human mind is tricky. :D
Yeah, sometimes it's easier to avoid something completely than doing it in moderation. I personally don't see any point to masturbate in moderation if you can easily live with it for weeks or months, it will rather undermine your discipline than give you some benefits.