You can but they can constantly scan for any open connection that happens by and then dump cached data into it when one is found. Cell modems are becoming cheaper too, as is bulk cellular bandwidth, especially if buffered for periods of low utilization. In those cases, it might be less data since the connection is limited or the data harvester is paying. People with basement laundry rooms will have a built in advantage when dealing with this sort of thing.

Yeah, unless it has a cell modem, not that it's cheap enough to make sense today