Well the movements aren't the ONLY reason. Maybe you can't tell the difference using Acos but what about TMY or, better comparison yet, HP5? The larger negative can let you use a faster film without penalty though, to be fair, the slower lenses and decreased depth of field means you stop down more too. Plus the larger camera makes you shoot slower and that can improve your images. Of course you CAN use a medium format like that, and something like an RB67 encourages it, but with a rangefinder (or my light little Yashica TLR) you're more likely to shoot quickly, which is both an advantage and disadvantage.

You can also crop the heck out of the 4x5 and still have enough negative for a good quality print.

The final reason is that it's just plain fun to use a view camera.