Hi Rob,
A couple of reasons I suppose - a linear actuator gives me full adjustment of stroke, with the same mechanical advantage and speed in any position. I also really wanted to avoid flexing the wire and very much wanted to keep it straight. I did consider a cam, as I did for my point motors etc which also accommodate microswiches, but I wanted to try these flip motors with the threaded rod to see how good they were. I certainly want a pause at the top, so it looks less 'mechanical' (the point motors have this facility, but one would need a very big cam to get the travel!)