Galaxy S4 Android lock-screen and phone wipe?

I have the paid version of FF on my S3, and no lockscreen needed. But with one of the ATT update nag messages, I finally caved, did the " update", and ever since, ATT blocks any tether ap fromworking, unless I pay for a larger data plan (mine is 2gb/month, no rollover, but I never even came close to exceeding it). But thats not the point of my post.

I bought a rooted S4, installed FF, and it works, and without using a lock screen. Why and when did they start with the lockscreen? And why does my s4 work without it? Puzzled.