Customer service tends to scale linear to sales, while engineering may or may not, so it gets pretty impossible to run a massive company with few employees without being massively hands off.
Engineering definitely scales sub-linearly to revenue (unless you're a body shop), but it's definitely always still above a constant. Large tech companies would be crazy to keep their engineering teams artificially low, because when you're making billions in revenue the added headcount ends up paying for itself even if it's only capturing that last 1% of possible product efficiency gains. Like, Google Search could be nearly as good as it is now with 1/20th the engineers -- but that last bit of improvement is still absolutely worth having the much bigger team.
