It all fairness theres not much logic to Star Wars. I mean the four heroes run around the Death Star killing stormtroopers for god knows how long and no one notices? So much for security. The difference is that the film is a goofy swashbuckler, whereas the PT are (supposedly) more realistic "dramas", so the suspension of disbelief is much less forgiving. Plus, the downright lovable charm of Star Wars not only distracted you from such petty matters, it made you not care if you noticed.

A very telling anecdote: they are filming the scene where Han and Luke and Leia are getting out of the trash compacter and taking off their stormtrooper outfits. Hamill suddenly ponders, "hey wait a minute, this doesn't make sense, how come my hair is all neat and everything?" and Ford simply replied "Hey kid, it aint that kind of movie."

I think that sums it up nicely.