It was the cry of the soul, or really interesting technical details? )
Briefly, the reason is quite technical, and it sounds "savings".
Next should be a phrase like "reduce the cost of additional equipment, we achieve reduction in the cost of our services." As an engineer, I can't judge how much truth in it, but logic dictates that some correlation needs to be really.
In General, block the subscriber of the mobile Internet is possible in several spots, and the oak, but effective and cheap, requiring expansion of network nodes, that is as seen in: the money ran out - the Internet was gone prior to re-registration in the network.