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

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.