..because the base characters come with no clothes, hair, etc..;) You can get hundreds of free Poser addons, right here in our Freestuff section, and also on the Web. I guess it's the same reason folks buy so many real clothes IRL, because you want variety.
As for where, look in the 'top 15' section on the right. It's actually more like top 1,500. Some links are dead, but a lot are not. Go there, look through their links, and just surf around. A search in Google on 'Victoria' and 'Poser' should bring up a gazillion.
You can have a lot of fun with the free stuff, so don't worry..go at your own pace..

I wish I'd said that.. The Staircase Wit

anahl nathrak uth vas betude doth yel dyenvey..;)