Because Adobe itself cannot come up with a good tool,that would make html5 "flash like" projects as easy to develop as flash projects.
I work in an agency and we stopped doing this kind of work. It takes way too much time to come up with something average. Someone will come up with a real solution eventually , just not Adobe.
Edit: In the interest of not being a negative prick, this is something by the same developer that I love: http://codepen.io/rachelnabors/full/lqswg