It's not really up to the curl people to rewrite it in rust.
It's for the proponents of rust.
Personally, I'm largely convinced that writing in rust will lead to safer implementations... now I'm just waiting for the full-featured, well-though-out, stable, useful rust implementations to appear.
I'm not married to curl. Where's "rurl" or whatever? If it exists and does something useful as well as curl (or better), I'll happily use it.
Well, curl is a bit of swiss army chainsaw for protocols and in general there is rarely a need to have same subsystem (of "downloading/sending something to an url) have support for protocols from HTTP thru IMAP all the way to LDAP.
So there is really no reason to use it Rust, use smaller, protocol-specific libs, less security problems and if you need multi-protocol support just switch by protocol and maybe write some wrappers.
And for calling it from C, "Rewrite it in Rust but make ABI C compatible" means you have to repeat a lot of Curl's idiosynchracies all while recreating all of the functionality. Looking at https://curl.se/docs/security.html there isn't that many of them that Rust safety would prevent so the real gains from that aren't probably all that great.
It's for the proponents of rust.
Personally, I'm largely convinced that writing in rust will lead to safer implementations... now I'm just waiting for the full-featured, well-though-out, stable, useful rust implementations to appear.
I'm not married to curl. Where's "rurl" or whatever? If it exists and does something useful as well as curl (or better), I'll happily use it.