Notice how they are both in focus, but if I want to blur out the background I would have to rack focus back and forth between the two of them. If I were directing that scene, just as an example, do you think it would be worth racking focus to the wife, to show emotion, or would it not be worth it since you cannot see her face, compared to him?
Worry about the script and the performance of your actors. Get those two parts right and your audience won't give a crap about the rack focus.
When you have a budget and can spend the time and money for a crew, THEN worry about the rack focus. The rack focus is like the cherry on top. Worry about making a good cake first, THEN go get the cherry. Nobody wants a crappy piece of cake with a cherry on it.