We reuse water daily.
My husband takes a bath every morning. After he is done, little Holly gets in. Usually Oak and Rowan will share bathwater as well. Apple and I still bathe together of course, she's still just a babe.
Also, I'll use bathwater for hand washing. We do have a washer, but occasionally we've been very tight on power, do to days of cloudy weather. There have been many times I've had to wash necessary clothing by hand, including diapers. In these instances, used bathwater is perfect for a wash load. Horrible for my back, but what can you do? I've never gotten the hang of EC.
Also, I use second-hand water for bathing the dog and cat (yes, I have to bathe the cat, Bristlecone is allergic, so I have to tend her coat in numerous ways).
I also will use bathwater for watering plants (we use natural soaps, and after reading some random articles about using a little bit of dish soap in your watering can = happy healthy plants, we decided to give it a try), they love it.
I think that's about it... then it goes into our gray water drain, to water the outdoor plants.
I agree that *leaving* bathwater is too much of a drowning hazard though. No water is that expensive.