Nice find! I think if people are planning to write commercially the 'don't bore us get to the chorus' mentality kicks in. After all, A & R are gonna spend 10 - 15 secs weighing up your submission and I'm not sure if that is entirely made up of an intro it'll impress them. In some cases the intro can be used to float a main hook or melody (even if only in 'nahs', 'heys' or 'ohs') as early as possible
I don't necessarily think an intro has to be any great length to work - the drum intro in Land Down Under is a perfect example (short, snappy but memorable and packs a punch).