Trust is really the main motivation in a lot of these situations. Imo, the value of “networking” in business is building trusting relationships with other people. I’ve gotten jobs by referrals from others, and helped other people get jobs via referrals. In those situations the referred candidate had an enormous advantage over the candidate off the street, but it’s not a system of buddies looking out for each other. It’s a system of people who’ve spent time establishing trust with each other.

It's the same reason why friends set up friends for dates. If you go "public" with apps, you can be setup with literally anyone. It often doesn't go well.