Most social media services actually require an email address to set up in the first place. Also consider that it's not the 1980s. If Grandma is 65 then she was born in 1956. When she was 14 the first email was sent. Computers took off when grandma was 24 and became pervasively including being part of most people's working lives during the time frame when grandma was 34-44.

This grandma and people older than her represent only 15% of the population and at this point 99% of them have emails. In 10 years. In the next 10-15 years half of grandmas confederates will have passed on further shrinking the population of non email users towards virtual insignificance.