I can think of at least one reason. Copy-pasting from a terminal fails to preserve tabs, while commas are fine.
Tabs might be somewhat less frequent than commas in data, but you're still gonna have just as bad a time when they do turn up. And don't forget quoting and escaping. Without proper parsing you can neither read CSV nor TSV safely. My go to solution is pandas.read_table()
Yeah, this is the deciding factor for me, too. The point of delimited text files is to find some compromise between machine-efficency and human readability. CSVs are generally much less readable than TSVs, but have less ambiguity, too. With TSVs, it's hard to tell if a tab space is actually a tab or just multiple spaces.
And with developers (especially Python devs) setting their text editors to translate tabs-into-spaces, copy-pasting TSVs results in data corruption. Or even opening a TSV in your text editor with default settings.
Tabs might be somewhat less frequent than commas in data, but you're still gonna have just as bad a time when they do turn up. And don't forget quoting and escaping. Without proper parsing you can neither read CSV nor TSV safely. My go to solution is pandas.read_table()