You wonder why unlimited mobile internet is always limited? The FUP boundary is not the only opportunity for mobile operators to "strangle" the transferred data.
There are other phenomena such as slowing down or shutting down some of the phone's features that are used by operators around the world. The biggest scarecrow is a hot spot for them.
They are afraid you can replace hard with mobile internet. Still, there are countries in which operators do not have that fear, and unlimited mobile internet streams come to an end.