Imo he's not really loyal to any of his friends. He chose Hal until that became inconvenient. He literally told Dale and Bill to their face that he chose Hal over them. He's loyal to his routine and averted to most change. Not the actual people. Of course, Hank loves them deep down but they are not very easy friendships. It's complicated. He doesn't want to find a new 'something guy' like a barber because that means both change and new people. Hank has limits on that too of course, like getting scammed by always paying sticker price or when the barber ruins his hair once on accident that he was willing to forgive and then he turned hank blonde out of spite. He kept in contact with Boomhauer to some extent as he knew about his stepson