What is CSV?
CSV is the least glamorous and most durable data format there is - rows of values separated by commas, readable by every spreadsheet and database ever written. Its subtleties are all about quoting: a value containing a comma has to be wrapped, and a quote inside that has to be doubled.
What is HTML?
An HTML table is what a web page shows and what a browser copies to the clipboard. It carries structure a plain grid cannot - merged cells via colspan and rowspan - which is exactly the part a converter has to expand back into ordinary rows.