Yes but if you need to have different shapes of collision in different frames, how would you achieve that with a fixed sprite attached? Then you would have to create all different boxes and attach/detach them at each frame, or attach them all and test each in each own frame of animation.
Or for example, I have a sword, and its polygon need to change angle at each frame. I cant achieve this even with imagepoints, unless I have 2 imagepoints to calculate the angle between them and reposition the polygon before testing for collision each frame.
Is that what spriter actually does? How does it achieves it, with containers, or it generates the event sheet code for collision?