Who said that risk wasn't considered? I've been doing this successfully since 1996, without any magical skills or unusual intelligence. I personally probably make 12-15 trades a year, I'm not talking about day trading.

Passive strategies have costs as well. Ask somebody with all of their money in VTI from 2001-2006.

Educating yourself and being opportunistic about seeking best value introduces risk but also unique opportunities. Personally, I like to realize gains over time and keep them liquid until a good opportunity presents itself.