That involves a different law. This case is about what happens when you enter an establishment, take a product and refuse payment.

Phone companies and other utilities use the protections of the well established credit reporting system. And they accept the risk of delayed payments in order to retain a long term contract. They could charge customers with "theft of services", but police generally would only interview you for a report, send it to the prosecuting attorney, who who decide whether to press charges. A court case would nearly always cost more than the bill, because there's always a grey area.

The cell phone company also has the protection of listing your balance as an uncollectible receivable and taking a tax deduction. They could also issue you a 1099 so you'd have to pay income tax on it.

Or they could sell your debt to a collection agency.

Retail establishments generally don't have the volume to fall back on these options. Face-to-face theft will always be a more severe crime than not meeting Net 30 terms. These places don't front anyone anything. You can't take their product and leave without paying.