I wonder if part of what David Chase was doing was showing that Bobby, while growing up in the life, didn't have the sociopathic tendencies that the other bosses had. Tony, Johnny Sack, Phil, even their soldiers had the sociopathic streak (taking joy in some of their kills, enjoying the notoriety of being a known killer, mistreating women) that seemed necessary to instill fear and keep the soldiers in line. But Bobby doesn't even want to threaten a union rep, doesn't want to do the murder Tony sends him to do, really just wants to play with trains and raise his kids.