That Welling is a control freak when it comes to his wardrobe but is a total yes man when it comes to all the crappy scripts says it all.
Welling is the same as 99% of all actors, he takes the advice of his agent. Actors act, they don't generally know shit managing careers or quality of scripts, so they hire professionals.
If the directors had a problem with it they could/would have negotiated with his agent. For example, if they truly felt wearing the suit or glasses would harm his future prospects, then pay him a significant bonus to compensate. Or completely refute the theory with evidence. But they just accepted it because that wasn't where they were going with the show anyway.