People building out a Sprinter aren't interested in fancy finishes. Many of those fancy looking ones are also built like crap underneath. Just good enough to look good and earn the maker a huge margin. Climbers, skiers, surfers that use them want cheap first and foremost. They want to conserve funds to buy time, not a granite countertop. They usually want to build it themselves to save money and customize it to their individual needs.
There's also a lot of people that build them that want to use reclaimed and recycled materials and minimize their impact on the environment. Those materials might not look fancy but they work and reduce the need for new materials to be manufactured.
Not everyone cares about how shiny things look or how impressed the other RVers will be.