Dreaad
Arcane
For the same reason that you're more friendly to strangers you find attractive rather than unattractive.
More to the point, I suspect almost everyone to a degree inserts (hur hur) themselves into the protagonist. After all regardless of the role presented to you, it's your perception of that role that shapes it i.e. you may be playing as a fat wood elf but that imaginary character is completely limited by your personal idea of what a fat wood elf might be like. Much like reading a book, the physical appearance of the protagonist, even if it's described in detail, will look different for both of us. Being able to choose that appearance can help you feel more natural in playing a specific role. Some people don't need this assistance and sometimes, if the story is linear enough, choosing your appearance can ruin the experience.
Generally speaking I dislike having underwear models like Shepard as my hero. I would much rather make some thug looking guy, who grew up on Earth in gang and is missing his left eye or something, it makes the story more believable as to why this psycho commander is going around punching people and committing genocide on aliens.
I wrote all that and said nothing at all. 
