1948 was the last year a major party nominated two governors (Dewey and Warren). Apparently as the Cold War developed, it was considered necessary that if the presidential nominee didn't have foreign policy/national security experience, his running mate should, at least insofar as Congress deals with foreign policy and defense--and besides, congressional experience is useful in helping the president deal with Congress in other areas. Hence Carter chose Mondale, Reagan chose GHW Bush, Dukakis chose Bentsen, Bill Clinton chose Gore, GW Bush chose Cheney, Mitt Romney chose Ryan, Trump chose Pence (a governor but with a background in Congress).
OTOH, if there was ever a year in which a ticket didn't need to have national security/foreign policy credentials, it was 1992. With the USSR no longer in existence and Islamist terrorism not yet a pressing concern, it was almost as though the US didn't really need a foreign policy...