This has been proven false a bunch of times, at least if the 1000s of people complaining online about it are to be believed. My google account is definitely old enough to vote, but I get the verification popup all the time on YouTube.
I think the truth is, they just want your face. The financial incentive is to get as much data as possible so they can hand it to 3rd parties. I don't believe for a second that these social networks aren't selling both the data and the meta data.