Why does MS-DOS use 8.3 filenames instead of, say, 11.2 or 16.16?

When I discussed years ago why operating system files tend to follow the old 8.3 file name convention, I neglected to mention why the old MS-DOS filename convention was 8.3 and not, say, 11.2 or 16.16. It's a holdover from CP/M. As I noted when I discussed the old MS-DOS wildcard matching rules, MS-DOS worked hard at being compatible with ...