Why didn't Ewan McGregor reprise his role as Obi Wan in A New Hope?

Alec Guinness was an ok replacement I guess, but I still don't know why Ewan didn't come back to play Obi Wan again. Was he unavailable? Didn't he want to wear the old age makeup? It's just odd considering that Hayden Christensen and Ian McDiarmid both returned in Episode 6. I know that Alec Guinness doesn't do conventions for some reason, but I'd like to ask him if he ever felt nervous about replacing Ewan at all. via /r/StarWars https://ift.tt/2FLTbNX