I do feel we are all entitled to have our own rules in our homes, but the matter does need to be broached tactfully.
Perhaps next time they visit, you could mention that you realise that social media are important, but you feel cheated because you aren't really able to talk to them, if they are using their phones and laptops all the time.
Say you would like half-an -hour that is "Grandma time" (substitute whatever they call you), where all phones and other devices are switched off, or left in another room.
This time is for talking! Strange old-fashioned activity.
Have something up your sleeve that you can tell them you did, when you were their age and do it with them.
Another good approach is to say you know nothing about Instagram, Snapchat, Facebook etc. whether you do or not, and get them to show you how to use these.
You may not want to use them, but knowing how means you can send them things and receive them and bridge the generation gap.