I think it's a whole new way of socialising now - one that I am very unfamiliar with! Stories about tinder and online dating apps fill me with horror.
Both DSs don't go out much but like your children, socialise over the internet. DS1's in a whatsapp group with his friends and they meet when doing various activities - volunteering, Explorers or clubs. He's got very good friends from an orchestra who live all over the country who he sees only at residential music camps. I think they get close quickly as they are all away from home, stay up late chatting and go through the process of pulling a concert together. He rates them as his best 'true' friends. Even though they don't see each other for long stretches of time, I really think they will be friends forever. They are in a whatsapp group.
Do your DC drink at parties? Mine don't seem to be interested at all and drinking and smoking are viewed with mild disgust by DS1.