One of the possible reasons is that they want to wipe off this traditional crypto exchanges that are not fully regulated and controlled by Governments, and they want to push people into using platforms that they have full control of.
The Idea is to get people to abandon bitcoin which they can not also control and then trade those ETFs on exchanges that Governments can control and manipulate any time they want.
That is basically their goal, it seems governments have finally accepted the fact they cannot make this market disappear, so they will try to implement next best option for them which is to corner this market and control it completely, I doubt they will succeed completely, however a great deal of the users will take the path of least resistance and will follow all rules and regulations set by the governments and use whatever platforms they recommend.