Depends on the field, but what I work on generally evolves so much over time that by the time I'm ready for a rewrite, the "edge cases" I had to account for when I started are either solved, partially solved, or can be isolated into some tiny part of the codebase that could be ported over from the previous code.

Beside, "rewrite" here doesn't mean "new repo, new project, new everything" it means reimplementation, usually based on the lessons learned from the previous implementation, and that does include edge case handling, as well as expanded functionality to "underwrite" or justify the effort spent on the rewrite.