Because its “left handed bindings” mess up my muscle memory for weeks: https://josm.openstreetmap.de/ticket/4760 . (It would be fine if that was the “side of the road” that all software “drove on”, but it isn’t, and I can’t adapt, back and forth. Yes, I’m kind of weak.) Too bad they hardwired everything, not knowing about indirection. Let’s hope iD doesn’t make the same mistake.