In my house you don't heat the water but it's been sitting in a metal water tank at equitorial latitude for hours so is generally quite warm for evening dishes.

Is it safe? Not for a restaurant where the temps need to get to parasite killing temps to pass muster.. but if I had to guess, the odds of getting killed by a bad-tempered cow outweigh it by 10x.

You're assuming an absence of solar hot water heaters - the world isn't homogenous.

eg. Our household conserves water (we track every litre we bring up to the tanks and filter) and we don't have a dishwasher - hot water is heated by the sun and run-off goes to the grey water tank for the garden.