I always wondered why the five who died a year ago in CoM have no servants floating around...

thetis_argent has my working theory: some of them haven't become crazed yet, like the Dancers, being exceptionally competent and obnoxiously good at swinging me around like a doll, remain obedient for probably up to two weeks after Demyx's death; others of them, like say Gamblers and Lancers, aren't actually all that sane, and would flail at anyone equally after their masters died.

The Samurai are personal. Xemnas's last insult. He's going to manipulate them for as long as he can...