UFA's goal is to make money yes, but they have artists who they have to be responsible for. Japanese music scene is not as degenerated as the US one, or EU one, where artists are caught shooting up heroin on a daily basis, or involved in gangfights [to exaggerate a little...] (Norwegian metal scene in the early 90's was marred by artists commiting murders, churcharson, and violence)
In any case, they have to show the Japanese society that UFA are in control, and are the bosses, and that they can handle a situation where one of their artists gets out of hand. So, in this case, we have Kago who is underage so far regarding the law of smoking, then she is caught smoking [breaking the law], and thus they have to react. Not only that, but I assume that it's not a very pretty image for an idol to be smoking, so they have to react on that as well. If she was 20 I bet the reaction would have been a public apology.
In effect, Kago's actions hurts herself, hurts the unit W, hurts the other member of W; Tsuji, and hurts H!P.
It hurts Kago on 2 levels: Careerwise and healthwise.
I never understood people who smokes, and Kago included-- your health is at risk. Is it really worth it, sucking on cancersticks? Just imagine if Kago was one of the very unlucky ones who got lungcancer? That'd be far worse than a suspension...
Anyways, my $0.2...