Not everyone had the same reaction to the scene. I think it reflects poorly on Luke's character that he could simply see the bodies of the two people who have raised him from birth brutally murdered and not even an attempt at burial -- pretty much the least of what he could have done. Agree with the OP's original post.
The film did not need to show a burial. That would have been nothing more than spelling everything out for the audience, which was not necessary. Luke's reaction to the death scene told the audience all it needed to know: he was shocked, hurt, then angered by the deaths, all successfully captured in Luke's expressions. He was still sad when returning to Kenobi, so there's no doubt about Luke's feelings.
This was the key transition to finally convince Luke that the Empire had to be stopped--an idea he was not on board with during the Kenobi hut/Jawas death scenes. Then, and only then did he look beyond Tatooine, and even the earlier "adventure" fantasies.