The thing with wifi is that you increasingly need a password to join. If a device comes with its own 4G/5G internet connection, it doesn't need your permission to phone home anymore.
Carriers offer bulk-pricing for manufacturers to prepay these SIMs so that they get service without any interaction of the end user. And the prices are so low for these telemetry/low bandwidth plans that it doesn't take too much potential monetization to offset the cost to the manufacturer. A big part of 5G is really enabling these multitudes of low-traffic devices to have low marginal cost on the network.
