I've always figured you for a pretty smart guy and, as such, should know that nothing is copyrighted until a copyright has been applied for and granted.
This is misleading. Registration of a copyright with the government is not required for copyright, it simply provides prima facie evidence of copyright allowing the copyright holder to collect statutory damages and attorneys fees.
In this country, the registration can even occur after the infringement has already occurred, allowing the copyright holder to sue for actual damages and lost profits.
So, if you think not applying for a copyright on a photograph means that anyone can take it and use it however they want, you are incorrect.
I believe the fee for registering a copyright is $35. But that isn't per image. I know a few guys who are still doing a lot of national news and celebrity stuff who register their work annually as a collection. So, everything they did for the entire year gets registered for $35.
Personally, I do not. The type of work I am doing these days and the way I have structured my fees make it so I am not really that interested in enforcing my copyrights. I make my money on the initial sale, then I don't worry about it anymore.
If I ever got into celebrity type work, that would change.