Why duplicate id

I often counter such issues :

1.      create a page
2. add a view to the page .
3. add a container to the page
4. add a view to the container
5. remove container all items .
6. create another view instance with same id into the container
7. duplicate id

My questions is :

.   When I removed the container all items ,the view should be destroyed . so when I create the view again it should be unique .

    I debug and found that  the view still exist ?

   Why .

   And more some cusomer controls have same issues .

    ex:

         A control   aggregate B control

        When render A control , I create a matrix layout cell  and add B control into the cell .

        Then you will find that  the B control will disappeared from the A aggregation properties .

       If you bind some properties on A and B , when model changed A will be re-render  then the duplicate Id issues will occur .