That engineer may have spent a couple of dozen hours on their mock. But the engineers who spent time on a test framework that uses real databases will soak up thousands of developer hours in CI time over the next decade.
That being said, of course, "it depends" on your use case. But I've found setting up this sort of test environment quite a bit easier now than writing database mocks, a lot less time-and-maintenance intensive, and relatively quick to run in any environment.
(Also, in a decade, I'm pretty confident this gap will get even smaller, while the time to maintain mocks will stay constant)