Most of the time the effect is just too tacky so there isn't a really high demand for it in the 2D pro graphics realm.
3D ends up using it a lot for more illustrative purposes (and for some tacky animations
The tough thing about building it into a plugin is that you need to position the control points, and a lot of the more DIY plugin people out there don't want to tackle the UI/in depth programming that you'd need for a morph plugin, and the pro's won't get paid enough since the people who pay for it won't use it.
I wouldn't be surprised if someone hacked one out for OS X sooner or later though (yay free developer tools!)