Why do guys add girls they’ve slept with on social media?

We talked lots, metteice, had sex once. He’s always initiated contact since for years, tried to flirt but I kept it friendly as I’m not into casual. So why would he add me on social media?
I personally think if you’re not hanging out in person then why connect online, unless there’s a plan to eventually.
Updates
+1 y
Sorry that was meant to say “we talked lots, *met twice*, had sex once, talked lots more...”
Why do guys add girls they’ve slept with on social media?
Post Opinion