Why is this a good thing? In the U.S., why should Democratic candidates for the presidential nomination waste their ads on Republicans who will not vote in the

Why is this a good thing? In the U.S., why should Democratic candidates for the presidential nomination waste their ads on Republicans who will not vote in the Democratic primaries? "The company’s advertising networks are limiting election ads audience targeting to age, gender, and general location (postal code level). This includes Search, YouTube, and display ads that appear on third-party sites. Previously, Google’s basic political targeting in the US allowed for ads to be served based on public voter records and general political affiliations (left-leaning, right-leaning, and independent)."