What sort of problems do you envisage having with an MIT license that public domain would fix?
https://sqlite.org/copyright.html
Including having their closed contributors sign affidavits and stored in a physical location. This may be what OP is referring to.
Compare that with an MIT license with no "hardening" like affidavits so that it's easy to mutate to another license type, I can see their point.
Interesting stuff since I never knew this "public domain" approach before!
* The author disclaims copyright to this source code. In place of a legal notice, here is a blessing:
* May you do good and not evil.
* May you find forgiveness for yourself and forgive others.
* May you share freely, never taking more than you give.
edit: thanks for the correction about the jquery license.
It gets even worse when you consider that there are MIT-like licenses, which can have fundamentally the same terms as MIT, but with slightly different wording. Then you can have to ship multiple variant license texts too.
Public domain (and public domain-equivalent licenses) you don't have to worry about this, because there is no requirement to include copyright notices or copy of license text.
I'm not saying you shouldn't credit people whose contributions you use, but you can make that a non-legal expectation of courtesy rather than a make-work legal requirement.