What if you had constraints on the CSV files? Suppose you knew that they don't contain spaces, for example. In that case, I don't see the problem with using UNIX tools.
Then you're not actually processing the CSV format, you're processing a subset of it. You'll also likely bake that assumption into your system and forget about it, and then potentially violate it later.
Well-defined structured data formats, formal grammars, and parsers exist for a reason. Unix explicitly eschews that in favor of the fiction of "plain text", which is not a format for structured data by definition.
