If someone was making a list of the most important American companies today, it’s unlikely AT&T would be anywhere near the top. It’s large, but not notably so: it came in 32nd in the 2024 Fortune 500 ranking, just above Comcast and below Verizon. Its offerings are not unique: it’s just one of many companies providing phone, internet, and other communication services. By market cap, AT&T is less than 10% of the value of Amazon, and around 4% of the value of Apple.But for most of the 20th century,...