Well I see it this way, if a character isn't of Caucasian descent a product doesn't sell, this has been done countless times and is still happening. Rarely does a character of colour get the spotlight... So, I assume it's fear because nobody does it and when they do, they get heavily criticized for it.
But than why aren't their works as equally publicized by the media?
I also agree with this^ and will admit to being one of these guys.1. Most writers in Western countries are white people writing what they know. Demographically speaking, it actually makes some sense for authors from predominantly white countries to write predominantly white characters.
To take this a couple of steps further - one reason that is occasionally given for the success of the glittery vampires is that the main character is only vaguely described. Therefore every teenage girl reading it can imagine that Bella(?) is just like her.
So my question would be how many main characters in fiction are actually white versus how many are in actual fact completely colourless and readers just assume they're white?
As said above, there could definitely be more representation, but I don't think the lack of it is out of fear. I'll add one author to the list Neal Gaiman and his book American Gods. The main character is black. It has won awards and praise out the yin-yang and has a huge following around the world. There are even rumors of it be made into a HBO mini-series.
[H]e was approached on an adaptation of Anansi Boys. Y'know, the book where the main characters are the children of African deity Anansi, and thus they (and a lot of their acquaintances) are black. The first question asked was apparently, "Is there any way we can make them white?"
I had a similar question a while ago, where I asked something like this:
"If I wrote two airship captains, both thieves, and not nice guys, basically supplanting a dark-skinned one for a white one, would it be ignorant of me to have them talk the same or would it be racist of me if I changed the dialogue to suit their proposed backgrounds?"
basically, I'm more afraid of being called on having my dark-skinned hero talk too "white" than writing him in the first place. Does that make sense? Because for me, I'd want my dialogue to sound like me... not like some terrible version of what I think he should sound like, making things up in my head because I have no real exposure to how people of different cultures might speak in a common setting.