Because some "edge" are not "edge", for example trading Beta. For real edge, you need to find Alpha, those "edge" should work in both up and down market. Folks who trade Alpha are the real pros.This whole concept of "edge" is really a ploy I feel like. Over time reading countless threads and ideas about "edge". Its just a term for consistently making money. Its 100% a hindsight bias problem. Nobody knows edge until it materializes, once its gone, that edge is gone. It can come back, how? Make money consistently again. But I just feel like we get into conversations too much about edge, we lean on that word way too much.
I traded Beta and for the past 10 years, until 2019, it worked great. Terrible drawdown in March.

Regards,