JW: You don't have a girlfriend, then?
SH: Girlfriend? No, not really my area.
JW: Mm. Oh, right. Do you have a boyfriend? Which is fine, by the way.
SH: I know it's fine.
JW: So you've got a boyfriend, then.
SH: No.
But when it was never supposed to lead anywhere, why the date-night scene. Why "do you have a boyfriend"-scene? A scene they liked so much that they used it both in the gay pilot as well as in ASIP?
was it only too show: "There will never be a relationship between these two"? why dedicating so much effort to it, that they sat down and said: "we gonna need a whole ass scene about it"?
Honestly, six years later and I am having so so much questions
Edit: This is even so much about "Why didn't they made johnlock canon" but more about: "Every scene has a purpose, and what purpose had this scene"?
John and Sherlock are already on first name basis by the time Lestrade comes around to Baker Street to ask for Sherlock's help.
Yet, when they arrive to Lauriston Gardens, this is how Sherlock introduces him to Sally Donovan.
And then again, this is how Sherlock addresses him once he has examined the body.
I don't think Sherlock did this unknowingly.
I think addressing him by his title is Sherlock's way of saying: "I'm not bringing you along because I pity you. You're not here as my sidekick, nor my assitant; you're here with me as my colleague (my partner, my equal). You're more than a wounded soldier who's been invalided home, more than a psychosomatic limp and an intermittent tremor in your left hand. You're a war hero with medical training whose opinion I value highly. I both respect and need your expertise because you're more than the sum of the bad things that have happened to you. You're still you, and you've still got a purpose in life."
Sherlock was basically showing John the battlefield he missed so much, giving him his life back, but at the same time, he was also offering a partnership where the two of them make up a unit.
Maybe John understood that too; maybe this is what he meant when he said "I was so alone and I owe you so much..."