While many people are now using 3D printers to make quickly reproducible pieces, not everyone has a printer or knows how to model. It's also relatively expensive to hire someone to do either for you. Sometimes you just have to make what you need to finish a piece and sculpting is really the best way to do so. There's also something to be said for digging your fingers into Monster Clay or Sculpey and bringing something to life!
It's not always about making an entire piece, either. I use Apoxie Sculpt on a regular basis to fill gaps or finish pieces like I did yesterday when modding a toy rifle for my oldest's TF2 Halloween costume. After trimming it down I was left with a gaping hole in the back that I patched with Sintra and molded over with Apoxie to create the right shape.
Your challenge today is to sculpt something using the medium of your choice: Sculpey, foam clay, Playdough, Magic Sculpt, mashed potatoes, or whatever floats your boat! I'll be working on Slimer tonight but here's a link to Polymomo Tea who makes amazing, kawaii minis and provides tutorials on how to sculpt them yourself!