Yes I wonder the same thing - I think about Apple and how many engineers they have which also seems crazy for their "output" in terms of product variations. Uber is on a whole nother level, at least from the perspective of the average consumer.
Not everybody works on customer facing products. Apple has a ton of software to manage their supply chain and other logistical things, which requires a lot of engineering effort. That’s what happen when you try to control every part of your product development.
Apple builds a lot of pretty complicated desktop software, cloud infrastructure, two popular programming languages and tooling for them, and even their own operating system, and their own hardware.
I don't think it can truly be compared to a company built around a single app. Even if that app is very popular.
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