[annowiki]

Its usually not so much "a range of wheels optimized for specific roles" and more "one size fits all."

You want a wheel that fits your cart. You have a lathe. Why make do with a wheel someone else made, standardized, and sells to fit a wide range of carts when you can make the perfect wheel for _your_ cart?

Most of the functionality in libraries use standard algorithms anyway. I doubt anyone thinks its a good idea to write your own cryptography or markdown processor, but why do you need a library to left pad a string with zeroes?

if statements and flags take time to process. You only have one way you need to do something. Do you want to take that much more compute just checking flags that will never change so you can get the library function to do what you always want it to do?