Because everyone and their grandmother misinterpreted the announcement to say that they weren't going to throttle anyone at any time anymore.
AT&T softened the throttling policy as per the link I posted. It's not a hard throttling no matter where you are when you reach 5GB.
Example. I was throttled as of about 6PM last night. No matter where I went I was throttled at AT&T throttled speeds. Throttled at work in Philly, throttled at my home areas South Jersey. Now since the new policy took effect I'm not throttled at work and not throttled at or around my house. My work is in a pretty heavy populated area in Philly located west of Center City. Now Center City Philly I might have a different experience since it's much more congested. I haven't tried it there yet.
Again the point is AT&T has softened the throttling practice. I'm NOT at throttled speeds at work or at and around my home. I've been getting advertised speeds.
Like I said I don't know what it will be like when I hit a congested tower/area or what the speeds would be. All I know I'm not throttled at the places I most frequent compared to before where I was throttled at .50Mbps down and up in the places I most frequent.
Those of us that still have legacy unlimited data plans our plans have gotten better without even lifting a finger
.