A Dangerous Place

Why makes this Joke funny?

Joke:
Restaurant bathrooms are really, really dangerous… So many of my first dates have gone to use them and vanished.

Explanation:
– Setup: “Restaurant bathrooms are really, really dangerous…”
  The setup here leads the listener to expect some sort of danger or risk associated with restaurant bathrooms, perhaps thinking of reasons related to hygiene, physical safety, or something else related to typical restroom issues.
– Punchline: “So many of my first dates have gone to use them and vanished.”
  The punchline defies the expectation set by the initial setup. The listener might be expecting an explanation about the inherent dangers of restaurant bathrooms. Instead, the punchline turns it into a self-deprecating joke where the humor comes from the unexpectedness and the implied awkwardness/rejection of first dates. It implies that the dates preferred to escape through the bathroom window (or simply leave) rather than continue the date, thereby subtly suggesting that the speaker is a poor date, which is not actually the danger initially implied.
The humor in this joke arises from the misdirection and the surprising turn from a general observation to a personal, slightly embarrassing revelation. It also involves a degree of relatability, as many people have experienced awkward or unsuccessful first dates.