So basically since MoI is not just 100% focused on 2D drawing but also manipulating things in 3D it can sometimes be hard to exactly replicate 2D workflow like you're asking about in cases where it would cause some degradation in being able to do 3D multi-viewport manipulations.

Aside from dragging, just the basic act of drawing it can be really useful to be able to pick the center point for a circle in one view and then pick the next point in the front view to produce a circle that has its center in some spot that was not easy to pick in the front view but still is oriented flat to the front view because of the second pick going there.

Basically this kind of combination of some picks in one view and further picks in another view can help out in placing things directly in a 3D position in many kinds of situations, the sort of "lock all mouse activity to the first view you clicked in" type mechanism like you are describing would have a side effect of removing all of that current multi view placement abilities.

- Michael