Knowing this information is very important! I had a director that I worked with in a local production that got on our case all of the time about moving around on the stage. You simply didn't need to move during the scenes if there was no reason. We had to have a legitimate reason to do so, and yes, the same goes for your characters.
A common flaw I see in writers, however, is the obsession of adding far too many of these reasons in for the characters. Before long, this character has become a counselor's dream client knowing he will be able to retire just with the income of dealing with all of the character's problems. In other words, not good.
I do think part of the reason authors do this is because they aren't thinking of the story in a global context. They are simply seeing the story as these individual scenes, so when it comes to a time to add motivation, the author is thinking of the single scene, and not the unity of the entire story. I also believe there are authors out there who believe adding each of these will allow multiple audiences to appreciate the story and tap into something they can relate to.
In either case, it becomes a distraction, and even more so in the case of a romance.
Let me give you an example of something I see far too often in a Regency romance. The hero, who we are supposed to be cheering for and wanting to get hooked up with the heroine is dealing with:
- A war injury, most likely a leg because we thought Patrick Swayze in North and South was hot with that limp.
- He has PTSD and frequently wakes screaming with nightmares
- The PTSD results in cases of E.D. every now and then and thinks he is not a "man" anymore
- His family is losing money due to a cousin who is spending the family's money.
- The heroine's dad has a hatred of people with blonde hair which he happens to have.
But wait, there's more. The heroine:
- Was abused as a teenager.
- Is protecting a sister from unwanted advances from the "Skank in the Ton" (sounds like a great title)
- Mom has migraines and does the Laudanum/Hops personal medical treatment.
- And she is a shy virgin!!!!!
And now we are going to add in the central story arc??? Really????
I say this over and over again here. KEEP IT SIMPLE! Pick one issue (I might give you two if I am feeling generous that day). Have them work through it. You might find the story flows better!