Because our binmen don't think so. I did think so because it's literally small, electrical, and an item.
I did as instructed and bagged it up (it fitted in a normal size carrier bag, not even a bag for life just a normal one from the co-op) and placed it on top of the plastic recycling box on the kerb.
They removed it, put a sticker on saying it wasn't something they collect, replaced it on top of the recycling and then didn't empty the plastics box at all due to my terrible mistake.
The magnetic info sheet we get every year with info about the bin day and what goes in what box just says to bag up small electrical items and then says "eg kettles, toasters, hairdryers, tablets, batteries etc". It's not really much bigger than our 4 slice toaster so I assumed it was fine!