You seem to believe that ICAO has the control over retirement age, which they don't.
I do not believe that at all.
Retirement age is set by the various participating states, not ICAO.
Right, I understand that, and have already stated so.
Several countries (including the US) could come out tomorrow and abolish all retirement ages if they so wished, and ICAO cannot, and does not, control that.
Agreed.
From an article discussing the age 65 increase in the U.S.
Although grounded commercial transport pilots have fought over the past decade to regain access to the flight deck, it was not until after the International Civil Aviation Organization (ICAO) last year allowed pilots to fly until they reach 65 that momentum built quickly to change the rule in the United States. Following ICAO’s lead, international flights would require at least one pilot under age 60.
....
After decades supporting a rule requiring commercial airline pilots to retire by their 60th birthday, the FAA earlier this year signaled that it now supports raising the retirement age to 65, matching the new ICAO standard.
....
On September 27, 2006, Blakey established a group of airline, labor and medical experts to recommend whether the United States should adopt the new ICAO standard and determine what actions would be necessary if the FAA were to change its rule.
I'm simply guessing (as in my own opinion) that, if ICAO changed their standard to have no limitations on age, that only then would the U.S. consider raising their respective limits. Of course it won't do much good unless all the other countries we fly to adopt it as well.