Wardrobes, many cupboards, chests of drawers, their kitchen cabinets, the infamous "Billy Bookcase" all have a back panel that is pined in place and need a hammer.

Sometimes the little wooden dowels that hold many sides in place need a small tap from a hammer to get them home.

It's rare, but it is sometimes needed. The 2 things I'm thinking of are some of the mounts for the screw-in adjustable feet, and the tiny nails on the back of cabinets and closets that hold the back on.

Sometimes you may need one when putting in those wooden rod things? Not sure what they are called.

I typically just use the butt end of the screwdriver when I have to put them in

Edit: didn’t see the other reply mentioning the same thing :(

You haven’t assembled enough ikea furniture then

Other than the backs of wardrobes and bookshelves that are attached by nails, IIRC you can occasionally find elements that need to be hit with a hammer to ensure full, tight fit - in those cases you want a rubber-tipped hammer though.

You need one when building a Hemnes or Billy. The back of the nightstand/bookcase is a sheet that you slide in and hammer in with nails.