It’s nothing more than a relative advantage that a few traders have. It is all because of the years they have spent learning.
%% Indicators are quite helpful; but trying to use both a 20+ 21 day moving average cross could work well but picking up pennies + slippage + there are so many better ways to do it. And turns out the old HI commissions were helpful in that those hi commissions forced one to get in the habit of some big trends.................................................................................................... Its fine if they are correlated , in some cases, but correlated like a 20+ 21 dma may disapoint mostly.
What a higher time frame or a higher MA can help you determine the overall trend. So on a smaller time frame what may seem as a downward trend is actually just consolidation within an upper trend.