[eluser]Colin Williams[/eluser]
A cart library has been in the winds for a long time. I think it's a good addition to the framework. And I don't think it bloats the codebase in any negative way. Like any CI lib, you aren't forced to load the file. I also think it serves as a good example for how libraries should be developed. Don't know if that was a goal or not. I think they just saw it as a useful tool to provide for CIers.
Although, I bet something like User Auth would be more readily received, and rejoiced by this community.