The purpose of the leap second is to preserve the international definition of the calendar day duration as one rotation of the earth while allowing the duration of one second to be defined by cesium.
The priorities chosen by each of the three groups above have been accompanied by lack of concern about the unhandled characteristic.
In 1970 when the CCIR decreed that leap seconds would start they had no algorithm for implementing them. It remains the case that the ITU-R has no responsibility for the ongoing implementation nor for any robust scheme of communicating the leap seconds to operational systems.
In 1988 when IEEE standardized POSIX they opined that computers do not keep precise time. Contrary to other cases where POSIX allows systems to implement a better scheme than required by the standard, in the case of leap seconds POSIX prohibits systems from doing the right thing.
The proposals to abandon leap seconds in UTC have not included text which describes the effect that would have on disconnecting the calendar from the rotation of the earth.
The documents from all of these groups have been silent about the issues that are not handled. Figuring out ways of handling the issues has been left as an exercise for other groups. The result has been that different systems have adopted different strategies.
Reading through the history makes several things clear. In 1948, 1950, 1952, and 1954 astronomers proposed, resolved, and explained that a new kind of uniform time was needed for technical purposes, but that the old kind of calendar time was still needed for human purposes. In 1955 astronomers voted to redefine the second to have a duration that is unrelated to the duration of one day, but they voted in a context which explicitly understood that there was more than one time scale which could be used to assign labels to points in time. While voting to define the second in terms of a fixed duration (in a time scale of Ephemeris Time or Atomic Time), they also voted that the radio broadcast time signals should continue to provide calendar days based on observing the rotation of the earth (in the time scale of Mean Solar Time, a.k.a. Universal Time, as had been internationally adopted in 1884).
During the 1960s astronomers pointed out that precision timekeeping with atomic chronometers means that there must henceforth be two kinds of time scales. The physicists and radio scientists adopted the notion that it was impossibly confusing to have more than one time scale, and they ignored the objections of astronomers who said that a time scale with leaps would cause trouble for automated systems in continuous operation. The physicists, radio scientists, and bureaucrats decided that radio broadcast time signals should have seconds defined by observing cesium atoms and days defined by observing the rotation of the earth, and they led the CCIR to adopt leap seconds in UTC. During the 1970s they lobbied various international organizations and nations to adopt UTC with leap seconds as the perfect time scale for official and legal purposes.
The result of those actions during the 1960s and 1970s is this:
Instead of international agreement on two time scales (each of which has clear definitions and applications) we have international approval of only one time scale (UTC) for which almost no two agencies have agreed on what rules apply for its definition and purpose.
One time scale about which everyone disagrees has turned out to be far more confusing than two time scales each of which serves a clear purpose.
An underlying premise for all of the time-keeping technology that horologists have developed during the past centuries is that it is important to agree on what time it is.
The saga of the leap second suggests that the parties involved believe that saying "No, we don't want to do it that way" is more important than agreeing on what time it is.