JKR mentions that Harry and Draco were never going to be even best friends when she discussed the way Draco is frequently romanticised
"“Draco,” writes Rowling, “has all the dark glamour of the anti-hero; girls are very apt to romanticise such people. All of this left me in the unenviable position of pouring cold common sense on ardent readers’ daydreams, as I told them, rather severely, that Draco was not concealing a heart of gold under all that sneering and prejudice and that no, he and Harry were not destined to end up best friends.”