It really doesn't have to be a van. Vans are common for several reasons:

• vans are the roomiest of common vehicles
• vans are nondescript which can help blend in when stealth camping
• vans are easy to find and buy

The #vanlife and #vandwelling hashtags are popular for a reason!

Cargo vans have additional benefits:

• they are usually white, which helps keep heat down in the desert regions where snowbirds are often found.
• they are bare (“a blank slate”) inside; nothing to remove before starting the build

Other platforms are RVs, cars, SUVs, truck campers, etc.