I think there's a difference between a blooper and a poorly staged moment.
I usually think of Bloopers as accidents that no one catches until its too late -- like the stormtrooper bumping his head on the door in ANH. Or maybe "movie magic" that fails in some way -- like the reflection of the snake on the glass in Raiders.
I think that's different than a bad shot like Luke's kick. Or poorly shot mechanics of the skiff shifting its weight from being hit by a laser bolt. Clearly they just didn't have time to do it again, Lucas watching his budget and all.
I mean, we don't say that lower budget movies suffer from more bloopers.
I could see time being a factor, but was GL still restricted by budgetary considerations when ROTJ was filmed? I mean seriously, between the ticket sales, merchandising, commercial tie-ins, etc., SW was making money heretofore unseen in the industry. I'd bet they could have afforded a second take.