The feature of software being maintainable and reusable by people other than its original author is for the users. It can be easy to forget until it’s too late.
1 file can be very maintainable. Reuse is promoted by a well designed library and interfaces, which can also be in 1 file.
Only thing 1 file can't do is allow concurrent work if bad version control is used. If patches are tight with good patch theory, 1 file is fine again.
Modern programming languages have namespaces, catch type bugs, all of it works quite well with 1 file. Recent OAuth Cloudflare 1 file library (coded a bit with AI) is a breath of fresh air, 2600 lines of data types and behavior in one place.
