I'm really taking this to the ludicrous extreme here, and don't seriously believe it (although i don't really know what to believe anymore) but if you had seen so many 'safety' issues brushed under the rug, why would you bother, when you know 'save 30% on our power bill' would be a slam dunk win?
Honestly though - 'more modern' is the wrong term for this. The technology for this to be a safe system existed in the 90s. Intamin's rapids ride (and i'm using Wonderland as an example here) had continuous load stations just like TRRR did when it was first built.
Wonderland's turntable was also switched off, I believe sometime in the late 80s or early 90s, and airjacks were installed to physically hold the rafts in position for load, unload and despatch. A series of infra-red beams were installed from the bottom of the conveyor to the top, at unload, load, and despatch, and the PLC was capable of monitoring the position of the rafts.
Operators had manual control of raft release at load and unload, but the PLC controlled the conveyor, and wouldn't release a raft into the unload zone while it was occupied. Further, A despatch jack would hold a raft from despatching too closely after a raft had already been despatched.
Picture below: Airjacks (metal frame with timber planking) to the right of the raft, and the despatch sensor beam (bottom left) mounted on the steel railings immediately below the loaded raft.
I know for certain that the conveyor had a beam across it to track rafts nearing the unload point, but try as I might, I simply cannot locate a picture of it.
Tales from the Wonderland Maintenance Bay:
As I mentioned earlier, the coroner made a point of stating right at the start that he found no fault with the ride operators. I agree totally disgusting, but very glad to hear they weren't faulted.