Conservative attitudes.
It is undoubtedly the case that it is difficult for the concept of PicMA procedures to gain initial acceptance among many pilots. As CRM experts have noted, "It is characteristic of human nature to question new and alien concepts on first encounter". The basic individualistic culture of pilots is built in from initial training, and constantly reinforced in proficiency checks and during career advancements. To quote Frank Tullo again, "A pilot would much prefer to be known as a 'good stick' rather than a good team member".
Consequently pilots want personally to hold on to the controls as much as possible. By definition, PicMA procedures involve two pilots sharing the "stick" time to achieve the common objective, rather than one being able to demonstrate superior skills, and much of the resistance to it comes from this purely emotional reaction.
So despite the fact that PicMA procedures have been in widespread use for many decades among a wide range of operators, there is still a huge pilot population that regards them with suspicion and even outright hostility. This is usually a gut reaction based on ignorance rather than a rational investigation of the facts. It is a true "cultural" manifestation: "it's simply not the way we do things. When it's my leg, I'll do the flying".
An anonymous Australian pilot commented some years ago on a pilot website: “I believe that those who refuse to consider changing the PF/PM system [to PicMA] do so mainly out of a misplaced belief that it would be somehow 'un-macho' to do so - an admission that they can't handle it all single-handed, as they've always done to date. The reason the procedure hasn't changed to something like the [PicMA] one much earlier, is that we pilots are without any shadow of a doubt the most conservative and resistant-to-change group in the world."
To paraphrase another pilot writing in 2014, "when I was with (Airline XXX) [a US startup airline] in the mid 2000s, I wrote and managed the low visibility ops program.... I had used the monitored procedure at TWA and AAL, and attempted to migrate that over to (Airline XXX). However, despite the official FAA position recommending this procedure, the (Airline XXX) Director of Operations would have none of it, and I’m pretty sure the FAA POI would not have, either."
Similarly, in 2014 the pilots of an long-established European PicMA-using operation with many low visibility approaches were told post-takeover by new North American management to "harmonise" with other parts of the organisation on PF/PNF procedures. The training and line pilots felt that their new management seemed to have a "macho" attitude that any pilot should be able to perform the whole approach regardless of other considerations.
The official reason given was that monitored approaches had frequently led to loss of control accidents, which would be now be avoided. The pilots were able to disprove this and retained the status quo - after pointing out that among things, deliberately changing AWAY from the FSF CFIT training aid recommendation on such flimsy grounds could expose the company and individual managers to legal action in the event of an accident.
An anecdotal comment from the managers of a large pilot website reflected that whenever PicMA procedures were raised, the subject generated negative comments from a vocal group that basically "monitored approaches were for wimps", and that these comments prdominantly came from the USA and the Antipodes. Interestingly, Ashleigh Merritt's research showed that respect for rules and procedures, reflected in scores on Hofstde's research in a "masculine/feminine" (MAS) index, was lowest in exactly those groups.
Merritt noted that "It may be that [high MAS pilots] view procedures and check-lists as unnecessary constraints. This attitude is borne out by the phrase "checklists are for the lame and the weak," a phrase heard when the author was observing some pilot training in the United States (the United States was ranked third on the pilots' MAS index)."
In reality, the vast majority of pilots in the many operators that have adopted "monitored approach" procedures have found it an eminently sensible way to operate that makes life much easier. However, having found it works well for them, they have no motivation or mechanism to advocate it to others - it is merely an effective tool that they use.
This is in fact the main reason for the creation of this website: as stated on the home page, operators are urged to "consider using monitored approach procedures" because of their advantages, but will then find there has been little material actually available for them to consider.