One should clearly differentiate between "networking" and "hanging out".

"Networking" is a constructive social interaction to establish or improve rapport with a contact, with specific work objectives in mind. For example, going to a professional meet and greet, exchanging business cards, and acquiring new contacts who can be resources.

"Hanging out" is a fun social interaction of limited professional value.

There are "introverts" and "extroverts".  Introverts prefer not to hang out.

Is the individual missing out - depends on whether there are decision makers material to their professional advancement and if they have a specific work objective in mind from this interaction, and whether it is the best strategy for achieving such an objective.

It may be that the individual's professional interests are better served by spending the "hang out" time, taking a course or getting an accreditation.