Well I'll throw my 2 cents in from a practical stand point.
1. I used to life a lot of weights when I was 17-19 (body builder). I would injure myself All the time. Then I started to stretch much more ... much much more. My injuries went way down. When I work out now I still follow the same thing as I did back then and stretch a lot; I dont ever want to tear an achilles, bicep or pec so yes I stretch.
2. As a chiropractor the patients that are the most flexible recover the quickest and are more likely to be able to have less long term problems and are less likely to have problems in the first place.