I think it might be because that self-reliance often comes with defensive language/attitude? It's one thing to be self-reliant and another to ooze a miserable attitude about it (e.g., "World's never done shit for me, guess I'll have to just look out for myself."). Without that outward expression, you don't notice that some people appreciate the importance of self-reliance without it feeling anti-social.
I think somewhere along the line "self-reliance" became conflated with "anti-social". I've had to put in concerted effort to build my social network of men I can lean on for social activities and accountability. Being by oneself can make almost any task seem insurmountable. Couple that with being self-reliant and you have a recipe for disaster. It is no wonder so many men are committing suicide.