If it uses a WiFi connection, it won't be of any use while away from one's home. It won't be of any use to those of us who park beyond the range of our home WiFi base station.
If it uses a cellular data connection, a monthly fee to the cellular data provider would be required. In the U.S., the AT&T cellular data fee was paid by BMW for 10 years after our 2014 i3 purchase. By refusing to offer a 3G -> 4G upgrade, BMW is likely saving money because it won't have to continue paying AT&T.