I wonder if it would have been seen as a sign of prestige for startups if yc had become a domain provider for .yc
Nobody uses those for their intended "national country" use. .io and .ai are tech-focused, .tv pretty much only has tv stations or video providers on it and so on.
Most of them do? I'm sure most .fr or .jp properties are operating in the French or Japanese markets. A handful of them (mostly the ones you list) have become trendy in other niches or provide opportunities for puns.
Even the "hacks".
Search "site:.ai Anguilla" for examples. You obviously be little reason to visit websites of Anguillan restaurants, government, telecoms, tourism etc but they exist. Within Anguilla it's a small signal of a local business.