That's short sighted as the only reason to do a Family Finder test is finding cousins and near kin within the last 500 years. As someone with Y-DNA non-paternal events from a Thomas Grogan I descend from in 3 different other families in colonial North Carolina maybe those people are trying to hide that type of information? Could be potentially embarrassing were it recent enough. Myself personally, I would have been disappointed were my Y-DNA test results indicative of descending from a person with a different last name than what was supposed to be.