With the modern web, the 'Internet of Things' and more and more essential business being moved online, the web is becoming a bigger and bigger target for attackers. Gone are the days when you didn't really have to worry about things such as security and HTTPS because it didn't really matter. You may also find that you are under legal obligations to protect your user's data correctly.
It could be expected that with all of this focus on security, especially in light of many of the recent massive hacks and data breaches, that security would be the focus of all developers; but that isn't the case. A lot of developers try to avoid it and if you are coming to Vapor from iOS it may be something that you have never really considered, especially since on iOS a lot of things are taken care for you.