There is little room for extremism when your society is the one "on top". Currently, liberal Western democracies and their vastly secular and sexually liberated cultures are the dominant societies on earth.

Conversely, many (but not all) of the most unstable countries have large rural populations, and the values of pastoralists, ranchers, farmers and wandering people differ greatly from those of comparatively wealthy urban centers. These countries are breeding grounds for extremist thought, be it through hyper-radicalized religion, civil war, post-colonialism, etc that we in the West don't often have to deal with.

So, your suicide bombers are almost by definition likely to be those from the largely rural, less-economically developed nations, rather than countries like ours.

Perhaps one day, an extremely repressive regime will come to dominate our society. On that day, perhaps you're more likely to see a suicide bomber in a mini-skirt. One man's terrorist is another man's freedom fighter.