Hello, Mage here!
I've been looking over all those "Herobrine"stories, and I think it falls into a category.
I call this category "Familiar Tune", it fits, doesn't it?
Now, are you wondering why Herobrine is so popular?
I've come up with a few reasons.
First reason, 
It has a good (bad) evil force to fight against the good guys, in which Steve is.
Secondly,
People enjoy action , and things alike in Minecraft animations.
(I, particularly, enjoy humorous animations, and good plot.)
Thirdly,
Herobrine, who looks like Steve, (I call Steve, Steven normally, gives off good vibes)
has white eyes, that glow. Isn't that cool or what?
As Fourth, 
Where did Herobrine come from? Some animators, do a sad backstory to Herobrine. 
(My personal favorite, is that Herobrine is Steven's dad.)
Fifth,
You can eat popcorn, while watching every single Herobrine movie/short , for the next three days.

That is a small fraction of the list I've made.
Now that you're all hating me, and judging me through your device, I'll tell you a secret.

I hate Herobrine
If you can't read that, let me type it again.
I hate Herobrine.
I you're still struggling to read it, I suggest seeing a doctor.
There I said it. 
This blog post was mostly to try and make me, Mage, enjoy Herobrine more than I dislike him. 
Sadly, I still hate him.
I hate Herobrine, Slendermen, and Frozen.
They all happen to be in the "Familiar Tune" category.
Before you rant at me, about the fact I've made a Slendermen skin, and Frozen skins, I shall explain why.
Alot of people enjoy those skins, and I make my skins for others to use.
So, if you're struggling to understand why Herobrine is popular, maybe some of those things I mentioned above will help you understand why.
Also, if you're open to anything, post below a comment or two. .3.