Except recently social networks, such as LinkedIn, takes note of any inactivity and will send periodic “enticer” emails in an attempt to increase you engagement with their site.
...straight to my spam folder.
The only reason I still have a Facebook account is "in case" I ever need to contact some of those old associates or school friends (a bit like hoarding old computer parts - I might need them one day!). I still have a LinkedIn account because I changed industry and thought I should at least have some way of contacting old business associates if I ever needed a way back.
Otherwise, I'd have deleted both accounts. They are of no practical use to me on a day to day basis, and I only hold on to them for a "just in case I need to contact someone" situation.
I did this a few years ago. Have a nice list. Never email any of them :-/