Command line flags?

Was watching [this curl talk][talk] from Daniel Stenberg and he included a graph of the number of command line options that curl has accepted over the years (around the 6 minute mark).

Got curious if there's any prior art/research/projects/attempts/thoughts on shipping command line software that rids the use of command line flags. Other than config files, I can't imagine what they'd be replaced with.

[talk]: https://vimeo.com/692145160