It would be helpful if the Project switch was remembered per viewport.
In 2d views it makes sense to have it on most of the time, but maybe not in a 3d view. If it was a per-view-setting, it would not be necessary to switch it on/off so often.
I for my part also tend to forget to toggle it on after switching to e.g. top view, draw lines, then back in 3d I recognize that the line was snapped anywhere in z.