Parentheses exist because it is the easiest way to represent the raw AST in text form. S-Expressions were originally an intermediate form for a more algol-like syntax[0], but became the primary form of representing Lisp because allowing the programmer to manipulate the AST is extremely useful, arguably what makes Lisp Lisp. There are homoiconic languages like Prolog and Julia that have more familiar syntax styles, but S-Expression Lisps are unmatched in making homiconicity readily apparent.

Another reason Lisp programmers tolerate parentheses hell is that Lisp development has often paralleled that of emacs and emacs-like editors that make manipulating s-expressions extremely intuitive.

[0] https://en.wikipedia.org/wiki/M-expression