I think the difference is that (the way it's presented, anyway), we don't really need to know anything more about John than we already do.  There is no secret.  His motivation was spelled out in ASIP, whereas Sherlock's was more of a mystery.

But John's violent anger towards Sherlock in TLD has changed everything.  Everyone wants to know why he did what he did, and the usual explanations won't help.  A look into his back story would answer a lot of questions, especially since, if the article I posted a link to above is correct, he apparently needs to make peace with at least parts of his past.  It's not only Sherlock who needs to come to terms with his history now!

 

Last edited by kgreen20 (January 15, 2017 6:41 pm)

On that last point, you may well be right.  We'll see.  But if that's the case, that's reason in itself for a 5th season!
 

kgreen20 wrote:

On that last point, you may well be right.  We'll see.  But if that's the case, that's reason in itself for a 5th season!
 

I see it exactly the same. There are many matters to explain, and hundreds millions of viewers, who want see the fifth season. 

Something came to my mind... The scene from beginning of TEH, when we can see John, and he looks different. He is wearing the coat, not jacket, and he has dark scarf. Later mrs Hudson reproaches him for lack of any contact, he nods, but looks so emotionally detached...  And his mustache - well, curls were not available ;[  I mean: did he made unconscious decision, in order to stop suffering, to become more like Sherlock, and stop feeling emotions? Can it be, why he gradually stopped to express his anger?
What do you think about it?