CSV has too many features. I recently found out the hard way that line breaks are allowed inside values, so you can't actually read CSV line-by-line.
Or maybe not enough features, because there's no other way to define a linebreak. \n isn't a thing.
And also, some editors are picky about the number of commas on each line. Excel and Sheets don't care if you have uneven number of commas, but IntelliJ's CSV viewer I think just looks at the first line to determine how many columns there ought to be.
Parsing arbitrary CSV is one thing, but using text files with field- and record-delimiters is another. When used as an intermediate data format, you can often get by with naive splitting on characters (especially if you use a less common delimiter).