vehicles that can be converted to have a pick-up kind of bed?

Hi, I know this is an dumb question but was there ever a vehicle that you can
convert back and forth between having some passenger seats and having
an exposed bed like that of a pick up truck?

For example, for some vans, you can get most of the seats out of the way for
maximum storage space. The problem is if you have to transport a really tall
object up right, the roof of the van will get in the way.

I know you can always solve this problem by pulling a trailer, but I am just
curious, as to why since most people don't use most of the seats in their
vehicles, why aren't there more solutions to convert them into more usable
transport space? thanks.