In my experience, it seems that a lot of people have an un-stated gut feeling that "doing something" must out-perform passive dollar cost averaging a broad low-fee index ETF.
If we came up with some obfuscated mathematical dance that, if un-obfuscated, were obviously dollar cost averaging in a broad-based low-fee index ETF, I think it would be more popular.
Edit: There are also lots of investment strategies where people are short tail-risk and don't realize it or properly account for it. For instance, my dad is a pretty smart guy (practicing medical doctor who never got his undergrad degree because he crushed the MCATs and got into med school after 3 years of undergrad, back in the 1970s when med school was less competitive) but he's convinced that his gut-feeling covered calls out-perform a simple buy-and-hold (on a non-risk-adjusted basis). I don't doubt it's possible to out-perform on a risk-adjusted basis, and maybe even on a non-adjusted basis with careful enough analysis, but he's never performed any analysis on the opportunity cost that he has given up over the years. Without any attempts to model or otherwise estimate opportunity costs, I doubt it's likely he's actually out-performing. He sees that most days, he's out-performing, and in the rare cases where his calls get allocated, he just tells himself "well, at least the long stock position did very well". He's short the tail risk, but essentially largely ignores that part because it's hidden by the gains in his simultaneous long position. He feels good because he's doing extra work, and most days he's out-performing, so the gut feeling is that he's out-performing the market on a non-risk-adjusted basis.