Although driving a LHD car is legal in the UK, insurance is likely to be slightly more expensive, overtaking is more difficult and dangerous, and any machine (car park barrier, toll booth, drive through) will be awkward to use.
You would think that with all the fancy FSD smarts these cars have, it wouldn't matter anymore whether it' RHD or LHD, as all the cameras and CPUs they have on board, could surely be able to let you know when it's safe to overtake and when not.
People don't want the hassle. But they're getting refunded, plus they're getting a good deal on a model 3 or Y. Some of them might choose to take the deal, some might not, but the customers are being taken care of.
It’s not just the ticket machines, the UK also has a lot of narrow country roads that are difficult enough to drive in a RHD, I cannot imagine driving a LHD in UK it would be hell on earth.
Perhaps, unlike tourists driving RHD cars, they're much more able to kiss the hedge on the narrow roads there without fear when other cars have to pass.