To me the reason is simple: this method is simply nonsensical! The line of the MA is an estimator of the equilibrum price. This means it is the best estimation of the fair value within your time horizon of trading. When you buy at the price just above the line you're buying a bit more expensive than the fair value. The job of a speculator is to find mispricing not to buy and sell at fair value. Money is made only if fair value shifts significantly. As an investor (not short term trader), if your fundamental analysis makes you confident the fair value will increase there is anyway no reason to wait up for the price to cross the line if you can buy cheaper right now.
No greed. No fear. Just maths.