The standard answer is that the US government broke up Ma Bell in the early 1980s to encourage competition. Hence the quid pro quo that had existed for decades

The standard answer is that the US government broke up Ma Bell in the early 1980s to encourage competition. Hence the quid pro quo that had existed for decades – you let us have a monopoly, we'll do research in the public interest – vanished. In short the fact that you can now make free long distance calls is why Bell Labs died. I wonder if we'll see a similar change now that the DOJ is going after Google for antitrust violations. Google has been very open about publishing many of their innovations (like the Transformer architecture), not to mention DeepMind's work e.g. the protein folding work that got a Nobel prize.