What were those guys smokin! Halle+ Tight restictive outfit divided by summer blockbuster=big box office
Well ... maybe that's what they said, but I have to tell you, believability in a role only rarely enters into the question. (Think Michelle Pfeiffer in "Frankie and Johnny." I'm reminded of the reason the producers of the "Charlie's Angels" tv show gave for firing one of the actresses late in the show's run. The official reason was "She doesn't seem smart enough to be one of Charlie's Angels. A friend of mine snorted, "Right. That's like being told you're not handsome enough to play Quasimodo").
Your observation regarding box office is on target. Usually (but not always), that's what drives these decisions.