Why? It seems that it would become inaccurate as soon as there's more than one contributor anyway. Can I just drop it?
The copyright statement isn't strictly speaking part of the license. Instead, it simply serves to identify who holds the copyright to the code and is granting the license.
In particular, it's perfectly possible (and fairly common) to list both multiple years (if successive versions of the code have been published over several years) and multiple copyright holders (if the code has been written in collaboration by multiple people or organizations). A perfectly reasonable copyright notice could look like this:
Copyright (c) 2022-2024 Alice Developer, Bob Collaborator & Zoe Contributor.
or like this:
Copyright (c) 2017-2024 The OpenFoo Software Foundation.
This software is based on FooServer 1.11b, copyright (c) 2011-2017 John X. Foo.
or even like this:
Copyright (c) 1998-2024 A. Developer, the Foo Project and multiple collaborators (see CONTRIBUTORS.txt file for full list).
The important part is that the copyright notice should allow the recipient of the code to unambiguously identify who has contributed to the code and may thus need to be contacted in case the recipient e.g. wants to renegotiate a new license for the code. Of course, in some cases this information may also be available directly e.g. from version control history, but the copyright statement should provide a more conveniently accessible summary of it even if the full history is not available.
The copyright statement should also include the year or years in which the code was published, to aid determination of when its copyright will expire and the code will enter the public domain. Under the current international copyright rules, where most copyrights last until 50 to 70 years after the death of the last author, this may seem somewhat pointless, and honestly it is of secondary importance. But it's traditional to include it anyway, it takes very little effort to do so, and it can at least be occasionally useful to determine how old some code is.
Ps. It's also worth emphasizing that, under current copyright law, a copyright notice is not required to claim copyright in a work. This used to be a requirement in some places, including in the US until 1989, but such copyright formalities are nowadays forbidden by the Berne Convention, which makes the establishment of copyright automatic from the moment a work is created (or more precisely "fixed" in a permanent medium e.g. by writing it down or recording it).
That said, the presence of a copyright notice can still be helpful if you ever wish to sue someone for violating your license, since it prevents the violator from using an "innocent infringement" (i.e. "I didn't realize this was copyrighted") defense.
Of course, if you're using a license as permissive as 0BSD, you're probably not planning on ever suing anybody for violating it (and in fact it's almost impossible to violate it in the first place). But should you ever decide that you'd like to switch your project to a less permissive license (like a copyleft license such as the GPL), a clear copyright notice would be much more important.
More to the point, for the recipient of the code, the copyright statement serves to indicate who has granted the license to the code and when. A 0BSD license without a copyright notice may leave the recipient uncertain about the validity of the license and whether it still applies to the entire code as they received it.
For a practical example, let's say that you're browsing GitHub and find a repo with a license stating just:
Permission to use, copy, modify, and/or distribute this software for
any purpose with or without fee is hereby granted.
and a warranty disclaimer, but no copyright statement.
Curious, you take a look at the git history and see that this file was added in 2015 by the original author of the code, Alice. Since then, Bob and Carol also contributed code to the repo, after which it was forked in 2018 by Dave, who refactored and extended the code before abandoning it in 2019, after which it was forked again in 2021 by Eveline, who fixed some bugs in Dave's code and also merged in new features contributed by "Fedor" and "Greta" and in 2022 transferred ownership of her fork to Harry, who is the current maintainer.
Confused, you decide to e-mail all the contributors, using the addresses recorded in the git history, and ask if the license is still valid. Messages to Alice, Bob, Dave and Eveline all bounce or get no reply. The addresses of Fedor and Greta aren't recorded at all, because Eveline rebased and squashed their contributions manually and the commits just have her address. Carol does reply, saying that she didn't really pay attention to how the project was licensed but she's fine with whatever, although if she gets to choose she'd rather prefer "something more standard, like Apache or GPL".
Harry also replies, saying that he hasn't really had much time to work on the project since Eveline handed it over to him, but he'd be happy to transfer it to you if you'd like to maintain it. And that he has no clue about the license notice, he just kept all that stuff the way Eveline left it, but he's happy to license his code "the same way as everyone else".
So, what do you do? And how much clearer and easier would it have been if there had been a copyright statement and if every contributor had updated it, making it look e.g. something like this:
Copyright (c) 2017 Alice, Bob, Carol.
Copyright (c) 2018-2019 Dave.
Copyright (c) 2021-2022 Eveline, Fedor, Greta, Harry.
Permission to use, copy, modify, and/or distribute this software for
any purpose with or without fee is hereby granted.
