The short answer is, "Why should they have developed?" We like to think of technological development as some static rate of change, or as a quantity which some invisible force pushes ever forward, a grand historical "given."In reality, we have no evidence or reason for this concept. When we ask questions like "Why didn't others advance?" we have to realize that we're expecting every society to behave like ours and, when they don't, looking for reasons to explain their deviation from a norm instead of discussing the factors that lead to how they really are. The field is best suited to answer "Why," not "Why not?"

A lot has been written on this topic, so I would recommend taking a look at these two posts from /u/RioAbajo and a former user. They're a good introduction to why the concept of "technological advancement" is problematic.