Why not participate in the Affordable Connectivity Program (ACP)??

I was surprised that the daughter companies, Metro by T-Mobile and Assurance Wireless both participate with Affordable Connectivity Program (ACP) but the parent company T-Mobile itself does not participate. Then to find out all the major carrier and most minor carrier competitors participate made me wonder why T-Mobile, who I have been with for years, was not part of this program.

When I asked while on the phone with them, the woman was confused by this as well adding it made no sense to her. She even went as far as asking her supervisor who had no answer for it. They did put in a request ticket for me for clarification on the question. If the ACP would eventually be implemented by T-Mobile at some point in the future.