> trip also knows where I live and vice versa.

Do those people also have access to your travel schedule? Mine don't.

Maybe you're just not as globally social as me? I've lived in 5 different countries and have friends all over the world and in probably 20 different US states that I can name off the top of my head.

Do I have close friends that I regularly contact? Do I send them a message when I'm in town to see if they are there? Absolutely. But it's not mutually exclusive with a cohort of people I will link up with when I'm traveling.

> well enough to link up

It seems bizarre to me that you only limit yourself to these people. I regularly try to meet up with people I don't know super well but want to get them or their city better. Social media has absolutely helped facilitate this.