When I visited Europe, I was impressed at how many roller coasters had a theme. I rode a portable roller coaster that had lasers, light effects, a waterfall, and real bursts of flame! Another coaster was a simple Wild Mouse that had a half dozen singing animatronic people. I rode a kiddie coaster that surrounded a huge robotic dragon sitting in a lake.
In the United States, most coasters do not have any theme. And the few that do have thematic elements often use trash and weeds like the scattering of stuff strewn around Apocalypse.