So you stop for gas in the middle of fucking nowhere, the vest doesn't get an internet conenction for veryfying your subscription and you are fucked, even as a paying customer.
It still boils down to a complex and much easier failing system, that could deny you critical safety features. I mean this also adds an entirely new dimension of hackability. Someone could hack into the server for the subcription verification and deliberately mess it up, or depending how poorly it is coded, could even access the vests of customers during their ride and disable them.
The system to trigger the airbag should never ever have a remote connection of any sort.