A bodkin is, essentially, a giant blunt needle for lacing ribbons and cords.
You’d think – I have giant needles. I don’t need a bodkin. I thought that for years, and then I bought one. It makes my life better. The “blunt” bit means that it doesn’t try to poke through the lacings, it just does its thing.
I’ll concede that if your necklines, waistlines, corsets and etc. do not involve ribbons and lacings, you might not need one. But if they do? You do. It makes feeding ribbon and whatnot so much easier and faster. My wardrobe features ribbons fairly heavily.
My red blouse lost its lace in the wash (not uncommon) and I needed to re-lace it before I could wear it. Before the bodkin, that would have been a bit of an undertaking. After bodkin, I had my blouse laced in mere moments.
The Dreamstress has a lovely historical article about the Bodkin and how essential it was for every woman back in the day where lacings were more common, if you’re into historical clothing, give it a looksee: