Joel Parker Henderson, on github.com:
You want your data content to be able to contain commas, or tabs, or newlines. You want your data content to be able to use data groups, or database tables, or spreadsheet grids. You want your data format to be able to use data files, or database schemas, or spreadsheet folios. You want a consistent compatible standardard format, which CSV doesn’t typically provide.
.CSV is the most common standard file format which is-not-a-standard I deal with every day. Usually you find ways around the different quirks — but for large files, it would be nice to have a more consistent flat file.