That's not necessarily true. Any projector can be used for mapping, it all depends on the size of the area and distance.
When you need to project across something massive like a cathedral from 100m away, then yes you're gonna need high end stuff like multiple 20,000 lumen Christie projectors using unimaginably expensive lenses, the correct mounting hardware and sophisticated control systems which edge-blend all of the screens to make one giant seemless image.
In the Smilers case though, they're using projectors comparable to what you'd buy for a nice home cinema set up, and they're fine because they work individually without edge blending, but the problem is they aren't locked down properly with proper mounting hardware. Vibrations coming from the ride above just knock them out of alignment straightaway.
...and there's also the cost of replacement lamps. I mean if they can't afford to keep fog machines topped up with cheap juice then they aren't going to replace projector lamps are they?
I wouldn't actually begrudge Towers using some simple projection set ups like that in Duel. It could work nicely and they wouldn't have to worry about vibrations this time around. Even if it was just some singing heads like in the Haunted Mansion. Nice little budget effect.
All depends how creative the creative team are. How about some screaming and dancing tombstones instead? Anybody could do that with a Raspberry Pi, cheap projector, and some Polystyrene sheet for about £200.
Does anybody here remember the screaming jellyfish in the Haunted House? That was one of the coolest, super low budget effects I've ever seen. Would be nice to see it come back.