More than likely they want access to your contacts for their spammy/scammy purposes. They might also use your accounts to promote their ⊗⊗⊗⊗ vitamins or penis enlargement products.
The one I see a lot in my junk folders are the notorious "Canadian Pharmacy" emails. They have been active for years.
I was almost a victim of a Facebook scam and I make it a habit to change my password frequently as well as secure my email and phone number associated to it.
I'm out of facebook too. But I manage my client's pages and it's not too hard to manage scammers. Fortunately they are few but the ones have clear fa.ke profile that some smart eyes can easily notice.