The argument against mixed use is often that they don’t want to be forced to live in a mixed use area, but the same people are fine with forcing everyone to live how they want. Most likely they only want single family homes because they have never experienced good mixed use and can’t imagine how great it is.
Wouldn’t it actually be water valleys? If you are standing on the shore and watched a boat go up a water mountain at the horizon it would stay visible, there would have to be a valley for the boat to disappear.