Most drawing programs that I know of (eg. Visio) give shapes handles in order to connect two shapes with a line. These handles allow lines to be "locked on" to the shape so if you move the shape, the line stays connected and moves with it; the two connected shapes are still connected after the move.
If you draw a circle, the application may place a handle every 45 degrees around the circle, which creates a problem of: What if I want to connect the circle at 33 degrees? I can't, unless the app lets me create a new handle, but that's the same problem really.
What is the problem that handles solve? I can imagine how handles would make things simpler on the programming side, but is it significantly simpler than allowing lines to be attached at any point along the circle? I am assuming this is difficult to achieve given that not many (or none) of the apps support it. Is there a difficult programming problem behind this that makes handles necessary? Or are we being lazy?