Legality aside, there are a not insignificant number of people who truly believe that private industry is invariably better than government at providing virtually any good or service, and that government involvement in anything that could be done privately is by definition harmful.
I actually had a conversation about this exact subject with a family member just last week. We live in a rural area and have awful service from Spectrum. He opposes plans for better cheaper muni internet because “The county government can only do better because they get to cheat - they don’t need to make a profit, but spectrum does.”
I personally think that a hybrid system is best. The government should build and maintain the physical infrastructure like fiber and cell towers, and private industry should be able to access this infra at cost + a small fixed markup and provide all other needed equipment and services on top of that infra.