In ancient times, the Jawas ran a huge corporation on Tatooine (Jawa, Inc.). They all worked in big office buildings. Jawa, Inc., was in the natural resources business, and it found a market for Tatooine's water offworld, eventually selling nearly all of it to the Galactic Republic and then the Empire. As a result, Tatooine became a desert world. All of the Jawas lost their jobs, there not being any market for sand in the galaxy.
The main traditions of ancient times that the Jawas retain are being in the natural resources business -- taking and selling droids and other things that fall out of the sky -- and working in large office buildings. To adapt to the new conditions on Tatooine, they put their office buildings on tracks and move them as needed.
Non-Jawas call the buildings sandcrawlers, but the Jawa word for sandcrawler translates literally to "movable office building."
That's my theory, anyway.
