According to the data from the beginning of this year there are now over 10 million bitcoin wallets.
You have to be clear, are you talking about empty wallets (with zero transactions), or wallets with a balance, or wallets that had a balance but are empty now?
I would rather assume that 1 bitcoiner might be using 2 or more wallets.
I use like 20 wallets at this point.
With bitcoin wallets being free and easy to create, it is illogical to think that multiple users are sharing control over one wallet.
Don't forget that the largest exchanges have tens of thousands of addresses just belonging to them. And that's with one exchange. And as you know, there are plenty. Then we have online wallet services, mixers, gambling sites, faucet sites, etc. The far majority of these wallets do belong to one of these services.