Must have more to do with individual personalities; on active duty in the USMC as a platoon and company commander and in the reserves as company CO and Regimental Embarkation Officer I worked with all branches of the service including socializing and I remember all concerned being focused on whatever the mission was and how to get the most out of it. Now this was back in the 70’s and 80’s and maybe things have changed, though my kids and grand nephews have all been in various branches and I don’t really get that much negative feedback. Maybe things are different at a higher pay grade, but I worked closely with Rangers and SF, Seals, Army Amphibs (LARCS), Royal Marines, and of course the Navy (amphibious and riverine) and we all played nice. Ironically the only really hard bitching I ever heard was in Panama at the Jungle Warfare School where the SF instructors had some choice words to say about West Point grads and the airborne as being aloof, arrogant and nearly unteachable.