IME shower caps are not that useful. I know this because I have just gone through my stash of complimentary hotel items to find a sewing kit and had to riffle through about 50 shower caps before I found one.
I always detach the shower head if I want to keep my hair dry while washing my body and when I wore rollers I found the steam in the confined shower cubicle useful for setting my hair.
I don't take them any more but being plastic they have a half-life of about 10,000 years so the ones I took 20 years ago are still pristine.
But that's just me. If you find them useful then you should take them.
I pity people like @Dummycrusher who sneer and tread on our dreams because they imagine their opinion will devastate us.
The first thing I do when entering a hotel room is to go into the bathroom to check out the toiletries. I've seen the pyramids but this is one of the abiding joys of travel.
On a business trip to Florence this month (all right, it was my husband's business I was his plus one) it was Jo Malone Lime, Basil & Mandarin. It was a posh hotel.
My top hotel freebies in no particular order are: slippers, body lotion, shower gel and soap, emery boards and orange sticks, sewing kits, cotton wool balls and tissues in handy packs.
I treasure a plastic but very realistic tortoiseshell comb from a hotel in Milan years ago. It's very stylish as you would imagine freebies from a hotel in Milan would be.
My mum liked Twinings English breakfast tea and small jars of Tiptree jam. Wherever in the world you are you know it's a really good hotel if they have jam from Essex.