Senior corporate leaders (C-level jobs like CEO, CFO, COO, Corporate Counsel) are usually recruited via an intermediary system of "executive recruiters" and "agents" who represent the interests of the candidates to corporate boards. Executive recruiters, attorneys and executive compensation consultants act as bargaining agents between the candidate and the board (which also has professional representation). Boards want to find a candidate who they believe possesses a fairly special set of talents, abilities and expertise. In order to get the best candidate - one the board likes, trusts and respects - they are willing to negotiate and pay more for the "right fit". A detailed "executive employment agreement" is negotiated between the candidate's agents and the board's agents.
Other than personnel staffing agencies who can (to an extent) represent job seekers in negotiating pay rates with a prospective employer, somebody seeking a mainstream job probably can't afford to hire an independent recruiter agent to represent them. Employers usually will not negotiate with third parties, and only negotiate pay and other conditions directly with the candidate. At the time of initial hire, there is some ability to negotiate pay rate, but for the most part what's offered to the candidate for pay, benefits and other aspects of work is offered as a one-size-fits-all "take it or leave it" proposition. There's no binding employment contract, only an "at-will employment" career opportunity.