[zrm]

Reaching the scale where it shows actual returns isn't all that difficult. You need it to happen 7.6 million times to save 1 CPU second, but each CPU core can execute it nearly that many times every second.

Probably you don't leave it generating only random numbers all day, but suppose you do generate a good few, so that it's 1% of your total compute budget, and you have only a modest load, using on average four CPU cores at any given time. Then saving that amount of computation will have saved you something like $15/year in compute, recurring. Which isn't actually that bad a return for ten seconds worth of choosing the right function.

There are also a lot of even fairly small entities for which four cores is peanuts and they're running a hundred or a thousand at once, which quickly turns up the price.

And even the things with internet scale aren't all that rare. Suppose you're making a contribution to the mainline Linux kernel. It will run on billions of devices, possibly for decades. Even if it doesn't run very often, that's still a lot of cycles, and some of the kernel code does run very often. Likewise code in popular web browsers, javascript on popular websites or in popular libraries, etc.

You don't have to work for Google to make a contribution to zlib and that kind of stuff has the weight of the world on it.