Just Cheney and Biden among VPs choosing not to run in recent times, right?
Cheney had his health issues
Using your standard that Biden didn't run, then more haven't than have. Mind you, it is unclear to me what you think are modern times. 2 of the last 3 didn't. 3 of the last 5 didn't. That brings us to 1988. 31 years count as recent to you?
Quayle, Rockefeller, and Cheney didn't run. Agnew didn't run, but I suppose he doesn't count. Barkley didn't run.
Bush, Gore, Nixon, and Humphrey ran.
Both of FDR's VPs before Truman ran - one against FDR for the Democratic nomination of 1940! The other, Wallace, ran for the presidency as part of a 3rd party ticket.
Mondale and Biden are in the group that did not run immediately, but did run.
Truman, Ford and Johnson became president before they could run as ex-VPs.