>>> And the primary reason is that one loses more in a single trade than what one probably earned in 5 or more trades.

This is the key. Once in a while, on the internets, I see people who say that they developed a strategy that can profit 5% month on month, etc. Excluding the ludicrous claims of 30% and similar monthly profit. However, they are often totally wiped out by a highly unlikely outlier event that should happen once in a century, as they like to call it. Or something similar.

The Black Swan: The Impact of the Highly Improbable by Nassim Nicholas Taleb is a good book on this subject.