How about these reasons:
1) Just now found this post because I have a working app with a working tree, and I've been asked to add a column, something I thought should have been easy, but your solution requires me to basically rewrite this whole part of the app to use a completely new control that expects the data a different way, renders the data a different way, and the events fired etc, are all different. All my RadTreeNode code is dead and has to be rewritten.
2) Your grid (in self ref mode) doesn't really look like the traditional tree people are use to. All I want is to display an extra column and to do that, you're asking me to rip out everything I've got working and start all over again, all because you guys are stubborn and keep kicking the can down the road. 2017 and still no winform treelistview.
3) I have some objects already stored in memory using a hierarchical and the RadTreeNode also is similar concept. The grid is not. I already have my code written that knows how to traverse the tree, insert new nodes, move, etc. Looking at your self referencing grid, looks like I would have to rewrite everything.
4) I would have to rewrite all the drag drop logic, dealing with multi check select tree, etc
5) So what if other people are using it? You are giving them no choice!!!!! The real question to those users is if they HAD the choice to choose between your self referencing grid and a proper TreeListView control, which would they have chosen then, and we BOTH know the answer to that, most would chose the proper control, the TreeListView.
People want a tree and they also want to show some extra data.
People do not want a grid pretending to be a tree.
Why are you so stubborn on this?