Social networks are not only visited by young people. And this has been the case for many years now.
The global average age on Facebook is for example 31 years old. And the 40+ age group is also massively present on the networks.
So, missing out on the potential of online advertising today means missing out on one of the most viewed and consulted channels, especially considering the fact that people connect to them almost daily.
Being on social networks today is like being in the phone book 30 years ago. That's where you're most likely to be found by your customers.