If you consider the work output of an engineer to be a proxy for value, then working for a machine that has extensive and significant capability for distributing value will result in more value creation (for you and them) than working for yourself would. If what you are building impacts 1B people who are paying in some way for what is being created, the value creation is way higher. The same applies to anything, more distribution power means more potential value creation and more value created. In a sense, you're more useful to a FAANG than you are alone.