If the report is true, this is the reason. It's a cost thing. Only Apple would have the numbers, but if a large majority of users only use the cable for chargin

If the report is true, this is the reason. It's a cost thing. Only Apple would have the numbers, but if a large majority of users only use the cable for charging, then it's easy to cut CoGS by including a cheaper cable. A secondary reason could be sourcing. I don't know cable logistics, but anything Apple includes with the iPhone means they need 100s of millions of them per year.