Several years ago, I noticed that in 'detective' novels, such as the Travis McGee and the Spenser series, the main character always had a secondary character who would do the things that the author needed to have done to advance the plot, but for whatever reason didn't want to write. So, if the main character needed to know who owned a car, he would call 'an old buddy in the Police Department' or, for details of a house's provenance 'a guy he knows in the County Board of Assessment'. I grew to think of it as a lazy way to avoid writing. (Sometimes, they did write it, and I always thought that was because they were being paid by the word.) In the Spenser novels, it's frequently Hawk, the brooding man of mystery who appears when muscle and excellent fashion sense are needed. He usually agrees with what Spenser wants to do, and rarely has insights of his own. Makes one wonder how he survives when Spenser isn't around.
Now, as I am rereading the Spenser novels, I notice that the more often the girlfriend appears, the more likely she is to say something which equates to Oh Spenser, you are so studly, so morally incorruptible, I swoon at your rugged jawline. To which he will reply with an insouciant quip.
Pity that the authors do that.