Character background is what happens between levels one and six.
-- Gary Gygax
"Character background is everything that's happened to the character up to the present time."
-- Me.
My definition is just as valid as Gygax's. In fact, mine's more valid, because it's actually supported by the dictionary:
"one's origin, education, experience, etc., in relation to one's present character, status, etc."
Background | Define Background at Dictionary.com
Gygax created D&D a long time ago. But now, his views on the game are no more valid than anyone else's.
The complexity of character creation created this need/desire to make character survivability a requirement. If you could knock out a character in 5-10 minutes without an online tool we would not be having this sort of conversation.
I don't know about other people, but, for me, the character builder is the last place I go when making a character. The first part of the process is a spark of an idea. Sometimes it's seeing a character on TV whose personality I like. Sometimes it's as simple as making an interesting race/class combination.
Then, comes filling out the personality. Is this person meek or boisterous? Do they follow their racial/familial upbringing, or do they rebel against it? At this time I'll also try to figure out why this person is the way he or she is.
Once that's figured out, I'll load up the builder and start putting together the mechanics of the character. Sometimes the mechanics will help me flesh out the character even more, especially with backgrounds and themes in 4E.
This is my process most of the time. Sure, sometimes I'll load up the builder and play around, and that messing around will result in a character I want to play. But usually, the character creation process begins long before the builder is even loaded.
So, yes, character survivability is something of a concern, because I don't make throwaway characters. Ever. Sometimes my process for making a character takes a week. Sometimes a few hours, and sometimes more than a week. I take forever to decide on a name, because that's a very important part of a character for me. I literally can't make a character in 5 minutes, regardless of the system, because it takes me longer than that just to think up the name. And when I put in that amount of work, I want the character to have a reasonable chance of sticking around a while.