Heretical Thoughts on "Winterizing"

I have a heretical thought (one of many, being a procrastinator, trained in the sciences, and somewhat averse to work that isn't needed):
Why is is necessary to add antifreeze to the various tanks under the Pod for the winter?
My general chemistry courses from many years ago learned me about the colligative properties of solutions (if you add particles to a liquid mixture or solution, it changes the physical propoerties of the solution). This is why a water and ice mixture is colder when one adds salt to the mixture. When water and water based solutions freeze, they expand. So we have the experience of pipes bursting in the winter (in the northern part of the country, I know this isn't a problem on San Padre Island!). However, pipes burst because the ice has no where to go but out, and so the pipe or tubing is split open. The same phenomenon occurs when one makes ice cubes in the freezer, only now the water can expand and the tray doesn't burst - because there is no top on the ice cube tray.
So, in effect the black, gray and fresh water tanks under the pod are large ice cube trays. We don't store them full to the top over the winter, most of us empty them completely - or as completely as we can. Therefore, any freezing of the contents is going to be of a minor quantity of liquid (and the black tank has a high level of particles in it and may not freeze until very, very cold.:) ) That means there is really not any problem with tanks bursting.
So why dump expensive pink stuff in the tanks, worry about contaminating the drinking water supply on your pod or making a mess of your hot water heater? Or keeping the black tank sludge in a liquid state?
The same could be pointed out about the water tubing. If one uses air to blow out the lines, thus emptying them, why fill them back up with the pink stuff only to flush it away in the spring? If you leave the faucets and shower open and the HW heater anode out, there is plenty of room for any residual water to expand and not burst the PEX tubing due to the pressure buildup.

Maybe I miss something, but we seem to spend hours (and dollars) winterizing and de-winterizing, when perhaps it isn't necessary.
Walt