R3-D3 was an Astromech who performed maintenance on the Starspeeder 3000. But then Star Tours closed and he was never seen from again. And he apparently never did a lot of work in the first place since he was always on break in the Droid Repair Bay. So apparently R3-D3 was a big lazy jerk who got laid off when Star Tours closed to make Star Tours 2. Serves him right.