There's somewhere in the ballpark of 166,000 employees at Apple, just unfathomable scale [1]. It is not unreasonable to ask that someone specific is responsible for each particular small feature and ensuring it keeps working. Trying to apply an economic analysis to such a "free as in beer" operating system does not seem to work well. Consider the question of "how many small holes can you have in your wooden sailing ship"?

[1] https://stockanalysis.com/stocks/aapl/employees/