I think people who drive those big RVs are kind of like the human equivalent of snails.  They move kind of slow and they always take their home with them everywhere they go.  And they probably leave trails of slime behind them, I bet.  

On the other hand those people do get to travel to a lot of national parks and I'm not sure snails do that.  Unless they're going to whatever the snail equivalent of a national park is.