Why just Truman?

There is a lot of talk about how Meryl was an actress paid to be Trumans "wife" and it got me thinking. So, if they had planned to build a fake world around Truman, why not do the same for his family (unless his parents were originally in on it anyway), closest friends and his future wife? It makes no sense to me that EVERYBODY in Trumans life would simply be actors. I feel like that's a pretty thin facade you know? The show already focuses primarily on Truman, Marlon and Meryl (as far as we see in the film) so wouldn't it make more sense to bring up Marlon and Meryl the same way Truman was brought up? Keep all three of them out of the loop instead of just Truman.

I mean, Meryl tells Truman how she plans to have a baby. How in the hell would THAT work out??? There would more than likely be a point when the actors playing Marlon and Meryl would actually want to live THEIR OWN lives or, I don't know, RETIRE? And for the actress playing Meryl, enduring pregnancy, childbirth and raising a child with, for lack of a better word, a co-worker is IMO about as far from the realm of any reality which I could think of.

They already groomed Truman, why not groom him a best friend and a wife as well?

"Let's get out of here before one of those things kills Guy!"