Probably because it often is too couched in ideals that seem for lack of better words childish - they already know that it is backed by a monopoly on violence and power vacuums tend to make any idyllic situations rare and short lived so there is little interesting there even to avowed anarchists. They're aware and usually consider it the lesser of evils unless things go /seriously/ wrong.
Better received are nuance and reality bound arguements. Talking about viable schemes to de-hiarch institutions and their limitations is far more interesting.
For instance one more viable concept is the "when everybody is the police nobody is" - a situation where everyone has the same policing powers and a tribunal legal system would be very radical but it is interesting conceptually to explore.
Specialization still produces premiums so one could discuss in said hypothetical if there was a "security fund" that people pay in and could get paid by consent for operating as a dedicated policeman despite lacking any privledged position legally. Even if one thinks the whole operation would probably be doomed to failure by collapse or hierarchy entrenchment it gives plenty to discuss in facts and opinions.