Because it would be more predictable, easier to memorize, less verbose, easier to use for developers coming from other modern languages and more comfortable to work with.
The fact that they are chaotic since 30 years ago is not a valid reason for keeping them chaotic right now.
Also, I'm not even arguing they should change the existing functions, that would break all existing code for almost no reason.
I think they should "simply" support methods on primitives, and implement the main ones in a chainable way:
"test string"->trim()->upper()->limit(100);
[0,1,2]->filter(fn ($n) => $n % 2 === 0)->map(fn($n) => $n * 2);
I would love this so much