The Allagans are the only society we know of that combined Magic and Technology to such a degree. And they made some of the craziest things imaginable. No other culture we've seen on Eorzea has come close to what the Allagans could do with either Magic or Technology, let alone the combined forces of the two. Of course, the Allagans also didn't have a morality check either and we know that Emet-Selch was pulling strings behind the whole thing too.

Which... actually might explain why we don't see magic and tech blended together either. Anyone with a decent sense of morality knows the Allagans got up to evil stuff with their amazing inventions. So I can easily see people associating "advanced tech" with "will cause you to lose your morality like the Allagans" and no one wants that to happen. Given how Garlemald has turned out (again with Emet-Selch behind it) it's not like history is proving that mindset to be wrong...