Why Isn’t Quo Primum in Effect?

I just read St Pius V’s bull Quo Primum. I’ve always heard that LatinTrad Catholics believe that this bull binds the Church at all times and in all places to the Tridentine Missal and the Roman Canon. So I read it and found this:

“Let all everywhere adopt and observe what has been handed down by the Holy Roman Church, the Mother and Teacher of the other churches, and let Masses not be sung or read according to any other formula than that of this Missal published by Us. This ordinance applies henceforth, now, and forever.”

And again:

We grant and concede in perpetuity that, for the chanting or reading of the Mass in any church whatsoever, this Missal is hereafter to be followed absolutely.

Here’s my question. There has to be a good answer from Pope John Paul II or even Pope Benedict XVI as to why Quo Primum is not effect perpetually, despite its apparent claim to be so. Anybody, know how Roman canonists explain the Missal of Paul VI?

Full text of St Pius V’s Quo Primum.