RVs

RVs are "recreational vehicles".  They are usually huge things, more like buses than vans.

Since they are complete dwellings, including living rooms, bedrooms, bathrooms etc. they are too large to drive during visits.
That is why most of them tow a secondary vehicle.  In this photo it's a small Jeep, but entire 4-wheel-drive trucks can be spotted behind these monstrous RVs.

The climate in the southern states also requires air conditioning and you can see two units on top of this RV.
There is an awning rolled up along the side.
Never mind how big the fuel tank has to be...