Comments and markups - stop things getting selected so easily

When using Adobe Acrobat comment markup tools - for example drawing a line, why can't the software ignore other existing objects? If I were to draw one line and then draw another off the end of it it won't let me! Instead it thinks I want to edit the existing line! Surely it would be way more sensible if existing objects were snapped-to when drawing new objects with a tool and only re-selected if the pointer-select tool is being used? Or am I just missing a setting which would turn Acrobat into a useful markup software??