i dont understand why anyone -guys especially- would not work out in some form. it makes you look better, feel better, and it is enjoyable.
me and one of my brothers lift and have put some quality mass on our skinny frames, but my other brother is boneskinny as hell hes 18, 5-11 120, i always try to get him to lift with me, try to get him to do something, tell him it would be so easy to improve yourself, but he wont have any part of it. just sits there playing online anime fantasy games all day long drinking coffee.
maybe im just way too appearance conscious, but i dont get why anyone would not lift, its so easy to improve yourself and there are no drawbacks that i can think of.