Draining fresh water (waste of water)

I sanitized our fresh water tank this weekend. We are normally in full hook-up sites but next week will be in a partial hook-up so we will be using our fresh water tank. I had to fill it and flush three times to get the bleach smell out. It occurred to me that I was just pouring 40 gallons of water out and letting it run down the driveway. I captured what I could in a 5 gallon bucket and carried it to the flower beds, lawn, etc. It would have been so much easier if I could have attached a garden hose to the outlet, but for whatever reason the manufacturer didn't see fit to install a hose connection. Does anyone know why they don't? I like to do my part in water conservation. I'm assuming it would be easy enough to rig something up, but that still doesn't explain why they're made the way they are.