Not about drag'n'drop specifically, but all kinds of interactions requiring a mouse-button to be pressed while moving the mouse, or dragging while keeping the finger pressed to a touchscreen. Considering how error-prone that is, and how difficult it is to aim at specific targets compared to clicking or tapping, I am curious how it has become so common to make this mandatory?
Anecdotally in older software it was much more common for instance to click on a thing to pick it up, then click again to drop it somewhere. Or to click the opposite corners when drawing a rectangle instead of dragging from one corner to the other. But in software today those kinds of simpler interactions are rare. Was the shift, if it was any, based on user-studies or what caused it to be accepted to use dragging instead of clicking?