After a spacecraft reaches orbit and jettisons its last stage, that stage would be in the same orbit too. What are methods to avoid this, or isn't it cared about?
In case of the Space Shuttle, the External Tank was jettisoned at an orbit that intersected with the mesosphere, so that the ET would reenter while the shuttle ascended on its own engines to a higher orbit. In the Apollo moon flights the third stage actually flew together with the CSM and impacted the Moon eventually (only the Apollo 12 stage entered solar orbit somehow). Did the 2nd stage of the Titan II GLV orbit together with the Gemini, and does that of Falcon 9 orbit with the Dragon spacecraft? Did the Atlas orbit with the Mercury?