"Unlike Git, you can check out only a subset of the repository."
Maybe useful, you can do that in SVN, also checkouts in GIT are very fast, the point may be moot.
"So I find CVS (and sometimes even RCS) convenient when the repository is a collection of largely unrelated files, and I'm more interested in tracking changes on individual files"
Ok, I guess it makes sense in this strict case (for example, a collection of config files). Apart from that, if you're wondering with version of file A works with which version of file B you lost.
"At least once, I've had to manually reconstruct a saved CVS file that had become corrupted. I'm not sure how I could have done that with SVN or Git."
They wouldn't have corrupted the file in the first place more likely... And yes there are ways to recover it.
Valid points; I never claimed that CVS is better than Git in general. I still use it for some things mostly out of habit and the fact that it's not really worth the effort of migrating (again, this is mostly for collections of files that don't depend on each other).
As for the (rare) corrupted files, I don't know what caused that. They were single-bit errors that I could correct by manually editing the *,v files. I know of no reason to assume that such errors are more or less likely with Git vs. CVS.
* Both are perfectly working versions of software
* Both have been obsoleted by newer, more fully featured, and more secure replacements (git cryptographically hashes its commits, cvs does not)
* Both have users that refuse to migrate from them because "it works for them", despite the benefits and impact on everyone else.