iOS JAILBREAK DEBATE

I just tought about something that I wanted to share.
Why aren't we modifying the iOS os like we used to rather than finding flaws in it?
Like we used to in ios 6 with ultrasn0w i believe it was called and redsn0w.
Just a debate, post your oppinions!

How are you going to modify a closed source OS?

What you listed are just jailbreak utilities and don't inherently modify the OS.