Yes, because on VMS (and presumably Genera) 20 versions of a file took 20× as much disk space as one version, so you wouldn't keep unlimited versions. In SCCS the lines that didn't change are only stored once, so 20 versions might be 2× or 1.1× or 1.01× the original file size.
Ummmm... yes. The problem with versioning file systems is that they only kept the last few versions; for files under active development, it was usually difficult to recover state older than a week or two.
(SCCS handled collaborative development and merges a lot worse than anything current, but... versioning file systems were worse there, too; one war story I heard involved an overenthusiastic developer "revising" someone else's file with enough new versions that by the time the original author came back to it, their last version of the code was unrecoverable.)
