Oh. So, two things are in my head that made me write that 1/ inversion (that is division) is one of the most expensive and ugly operations you have to do (remember we're dividing mod p where p is an outlandishly huge prime number). They did a ton of work on it. But 2/ is what actually matters here: they're careful to only expose in the API what a user of the library actually needs, because that lets them have the ability to change underlying algos without breaking software that uses the library. Some libraries have different strategies for that, like naming parts of their API "unstable" or "experimental". Actually come to think of it libsecp did have that kind of thing too. But anyway I guess it's just too low level and they don't want to be responsible for maintaining a stable API for that operation.