The actors in Truman's life must have been really heartless.
Take Marlon for example, and the same could be applied to all of the "principal" actors in Truman's life, he spends his own entire life playing this role as Truman's best friend and he never actually comes to love Truman and think of him as a friend?
Marlon, after everything started to fall apart, was acting like he didn't give a damn, that it was "just a role", well how can he possibly feel that way after being Truman's friend (even if it was an act) for 30 years?
That's not even counting Truman's parents, they may have been playing a role but they did indeed raise him from a baby, did they feel nothing for him? That theirs was just a role that they could walk away from without actually feeling love for Truman?
"Mr. Treehorn treats objects like women, man."