For about a decade, hackers have given the middle finger to over-controlling Apple by providing jailbreaks for iPhones. It was an endless cat-and-mouse game. Hackers would find a way to jailbreak the current iOS, Apple would get wind of it, they'd release a new version, and then the hackers would jailbreak the new version.
Rinse and repeat.
Jailbreaking wasn't just a principled stance that the user, rather than the manufacturer, should control what he can do with his own device.
It also created or unlocked iPhone features which made usage of the device far better.
Many of the innovations of the modern iPhone iOS seemed to spring from apps created for jailbroken phones -- ones you could download for free (or for a few dollars) from the underground jailbreak app store called "Cydia".
These features included multiitasking, the "swipe to bring down a menu which controls the phone's most used features", the flashlight (turning on the camera flash as a light source), the ability to tether (using your phone as a mobile hotspot), and many others.
Jailbreaking also allowed you to take more control of your phone for privacy purposes, such as allowing you to fake your GPS location.
However, as Apple got better and better at stopping jailbreaking, it became tougher. The public's interest in getting jailbroken phones also waned, as the standard iOS features expanded and there was less you were gaining from performing a jailbreak.
Eventually, some of the jailbreak hackers got frustrated, and left the scene.
iOS 10 has been out for awhile now, and there does not exist a jailbreak beyond iOS 10.2, which was made obsolete (and impossible to downgrade) awhile back.
Bottom line: For awhile now, it has been impossible to jailbreak any new iPhones, which usually come with the latest iOS already installed.
I have an iPhone with iOS 9.3.3, so my phone is still jailbroken. However, eventually when this phone breaks, gets too obsolete to continue using (it's a 5S), or the iOS becomes too obsolete, I will have to upgrade or give up on the phone.
That might be my last jailbreak, and I will miss it.
Most notably, I need the jailbreak to fake my location in order to watch Dodgers games on the MLB app, and that ability will likely be gone.
Here is a clickbait article which describes the situation: https://www.cultofmac.com/490594/jai...breaking-dead/