I would say the reason for that would be eg: eM Client has been working on V10 desktop and V10 mobile apps “which most users want to move to” and there is alot of testing etc with that which can take time, so “unless there is a major problem with V9” (where there doesn’t really seem to be from reading the forums lately), then V9 updates will be slower to update unless absolutely necessary.
But as i said, if you do have any current issues with V9, then suggest to create a new Thread of the specific issue and we might be able to help you with that.