Being friends with ALL the cast and crew seems to be a very odd style. I think it can complicated your relationship with an actor, and end up making you job more difficult - especially in situations where you may have to reprimand the actor. If your management style requires the actor "to be on your side" - or "do this as my friend", then it might be wise in how to evolve your management style - end of the day, there maybe people who don't want to be your friend, or you can't strike a friendship with. I find it odd that as a stage manager you want make it a priority to "be friends with all" and "socialize" with all - I don't have the time, energy or the interest.
I would actually encourage a younger stage manager to NOT socialize with the cast or crew - have a life outside of work. Come in, be friendly, social and work - but outside of work not involve the cast and crew. I think this can develop into a very healthy career pattern where your entire identity is not wrapped up in your career. As you become more comfortable with your management style and leadership abilities . . . then maybe you can socialize.
I like to, for example, take my team out to a meal during pre-production, drinks during tech, and then do the opening and closing parties - and that seems like enough.
I like having work relationships stay at work - which doesn't mean I am cold (those that now me) - I just find that regardless of how "fair" and "equal" you may try to be, it often doesn't work out that way.