Good points. Secrecy was once used so that people wouldn't destroy the evidence the warrant sought. But now it's easy to tell the third party to retain the evidence; even if you delete it, they can still keep a copy. So there is no reason not to tell the target; they can't change the outcome, but they can begin the counter legal process to ensure their rights are preserved.

Sometimes I wonder if they want secrecy so that criminals don't know they're being investigated, and commit a crime that's easier to prosecute. If they just stop committing crimes, then there's no fancy press release saying how great the DA is or whatever.