Self-contained base amenities keep troop spending from reaching host economies.

Evidence

In recent decades, the economic impact of U.S. bases has also declined as bases have become increasingly self-sufficient and isolated from local economies. Bases like Ramstein, with their plentiful food outlets, entertainment, and shopping, mean that troops and their families almost never have to leave base. In turn, this means most of their money never reaches the local economy. — David Vine, Base Nation_ How U.S. Military Bases…, 918