@LDRSHIP I suspect the same reason there are so many other common misconceptions about fitness out there. I mean, how many women still use 1–10 lb weights because they believe heavy weights will make them “bulky”? It’s absolutely not true, but people insist on “light weights, high reps” in order to “tone” their bodies. Lifting heavy is something men and women can do (barring any health issues) the same way and they’ll see very different results.
A very popular functional strength routine is Stronglifts 5×5. It focuses on only five exercises, but they’re compound moves that engage muscles throughout your entire body. It’s very effective for building strength.
There are people who insist on using machines and isolation exercises, but most trainers will tell you a functional training program is the way to go. It’s simply the most efficient way to work your muscles. Just stabilizing yourself while doing free weight exercises instead of a machine will engage muscles through your entire body, especially your core.