Andy,
Moving from cell tower to tower takes place within the control of one network operator, or in the case of international roaming, two operators who will have signed a roaming agreement and had their legal teams make sure all the “i”s and “t”s are dotted and crossed.
Moving from mobile to wifi network gets messy especially when the wifi hotspot might be owned by a coffee shop, shopping mall, hotel or private individual – in the event of a fault who do you complain to: network operator, ISP, barista? Furthermore, when you do complain, all the relevant parties need to have a mechanism in place to resolve that fault between them.
Technically, it's do-able, managing it all is harder.
Biting the hand that feeds IT
