Also for people who overload their bikes. I reckon by not having to lean the bike over it is considerably easier to mount. The latter statement is not evidence based....as I have never owned a step through bike. I notice though that when the rear of my bike is heavily laden and the front is unladen the front wheel has tendency to lift of the ground. I assume with a step through there is no need to lean the bike over??
No need to lean the bike over, but when I ride a step through I generally forget and do the same as with my bikes with top tubes.
Most step through bikes aren't very good with a heavy load. When carrying full rear panniers on the two step throughs that I ride occasionally (wife's bike for tests, visitor bike) I can feel a sort of "shimmy", this is with loads of 10-15 kg, so far less than my usual shopping load or long distance touring load with my own Thorn Raven Tours. But Thorn's 420ST design is more rigid than most step throughs, at the cost of a higher step through height.
I've just ordered one of the older Thorn 390S frames to replace the oldest of my visitor bikes on the island where we have a flat. The 390S is a bit smaller than the 420ST and has a lower step through height, so should be more suitable for my wife and for short visitors. I will probably be able to set it up so that I can also ride it myself for medium/short distances.