It can both serve a function (help build extended relationships) and be something people don’t want to do because those relationships can be severed in an instant thanks to at will employment.
And even if you or they leave, in many forms of business having friends in another company can be huge in providing a safety net or a path towards a better job. Socialization with others may be the closest thing to a union that devs have. If Amazon cuts your job, your old buddy who moved to MS might be a lifeline.