Not everyone is so keen on shopping, though, believe it or not, some of us are women yet still find shopping not much more enjoyable than any other utility activity (like clipping toenails). Especially if you have to drag small children with you, or guilty leave your DH in charge of 3 lively little beasts while cooing at the displays in Mamas & Papas.
And it's too early to even know which cute boy or girl clothes to buy.
Then you gotta find somewhere to store the new stuff, and then if the pregnancy does fall apart how to dispose of the new kit if you can't stomach trying again (well, MY stomach has declared no way ever again). So I might never get to use anything I bought and then I'd be kicking m'self adding up how much I spent for no purpose.
Plus, the later you wait to buy anything the more likely someone will just give you a good quality second hand version of exactly what you wanted.... or even offer to buy it as a gift new! (Or does that never happen with 4th pregnancies, I wonder?).
Not to say you shouldn't shop if you want to. Think maybe I admire someone who isn't purely practical like I am about it all.