In recent times, lock manufacturers and smart lock startups have replaced the wiring used in keycard systems with Wi-Fi and Bluetooth (or other wireless technologies such as Z-Wave or Zigbee). This enables smartphones to replace or support the keycards. Wi-Fi/Bluetooth replaces the wires and removes the need for an onsite computer/server to communicate with the locks and vice versa. The problems with Wi-Fi/Bluetooth and other wireless communication technologies, other than requiring a lot of onsite network infrastructure, such as modems/routers/bridges, is that they are insecure and can easily be hacked. They're also unreliable, there are pairing problems, blackspots, phones are slow to connect, and you need to switch on Bluetooth separately on your phone too, which drains batteries of the phone fast. Also with Wi-Fi/Bluetooth, the lock always has to be switched on and waiting for the programming or authorisation check, so it drains the locks batteries fast, or needs to mains powered. And if you have many locks, then you usually need to have a complicated Wi-Fi mesh system installed, not just your typical home Wi-Fi modem.
NB IoT overcomes all the aforementioned wireless problems as the network is purpose built for machines with no need for onsite network infrastructure, it has better built in security, and the lock can go in and out of different sleep modes to conserve batteries.