I have a theory about the conservative noise machine
Even better is "homicide bomber." The ostensible logic is that calling them "suicide bombers" is too sympathetic and touchy-feely, so we need to call them "homicide bombers" in order to remind everyone that these people are murderers. But the problem is that Americans have always been really been creeped out by the suicide angle. It's not like "suicide" in this context really brings to mind a depressed teenager making a desperate call for help. The media is full of discussion of what drives people to become suicide bombers because in American culture, the idea of embracing certain death in order to advance a cause just doesn't add up. This is true even when you divorce suicide attacks from the context of terrorism. Kamikaze pilots are a source of enduring fascination for Americans, but aside from the suicide angle, they were soldiers just like our own troops were. The suicide, and suicide alone, marks them as crazy. Using the term "homicide bomber" is not only redundant to the point of silliness, it actually defuses the reality of the situation. It's like saying, "You liberals think these are Kamikaze pilots? Ha! Real Americans call 'em Japanese Air Force pilots!"
Hence the conclusion that "homicide bomber" was actually proposed by the spinmeisters as a bar bet. If they really wanted to demonize terrorists, they'd call them "suicide fanatics" or something like that. But "homicide bomber"?