It's because the alcohol in the auto fuel absorbs it all...

Sadly, we still have to burn a fair amount of that over-priced blue crap
(that fouls my plugs and contaminates the earth) since most airports don't
sell mogas...

I've never found water in either mogas or avgas in our planes.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"