Perhaps you mean the only way they could maintain their monopoly? Bell Labs was Bell's bargaining chip with the government to allow it maintain its market dominance. The government allowed, at least for a long time, the monopoly to persist so long as Bell Labs was acting as a public good. As part of that social contract, Bell was not allowed to capitalize on what Bell Labs produced. I expect Bell Labs is so notable because the public at large was able to take their discoveries and turn them into productive ventures, to which they did. That's not completely unheard of today – LLM-based businesses being a recent example that stem from Google opening up research to the public – but it is unusual for today's research labs to give away everything. Today, not even the research labs with that explicit intent (OpenAI) are willing to give away everything (or much of anything).