Why didn't Kakashi take care of Naruto?
Being Anbu and a guardian to Naruto doesn't seems like a great idea. And Naruto was in the care of the Third, so it might not seem necessary. It is also to be noted that, Kakashi has a hard time connecting to someone emotionally too. And as per his past, he wouldn't want to get attached to anyone and wanted to be only an Anbu. It was the Third who removed him from the Anbu and assigned him with various teams as tests, as shown in the anime filler, and in the end assigned with Team 7.