No, it is not necessary that each user displays the status of usercontrol or webcontrol. it can be controlled during the page loop, if the viewstateproperties of the control set =false, then it will not be set until the page is returned. AutoPostBack
You can also control the viewstate properties of user control and web control during the pre_int lifecycle stage. you can also off tracing of view state in pre_int stage of life cycle. for more information link text