I have a very old pair bought in John Lewis but hardly ever use them and wouldn't miss them if they got lost.
I once had a pair, very stiff and not often used. They did get lost many years ago and I don't miss them!
As Greybird said, they were used when all machines were straight stitch, and only good for fabrics that didn't fray badly. Since I've had a decent overlocker I don't make many plain seams which need the edges finished but when I do I finish those edges with a 3 thread overlock.
The only other sort of thing I can think of for possibly using pinking shears is little circles of gingham to make pretty jam jar covers!