From my personal experience, I think even ICICI Bank and SBI haven’t completely figured out Joint Accounts yet. So Jupiter may need more time as it is quiet new to the banking game.
I am also wondering these are times where people like their freedom and privacy. So there may not be too many takers for couple accounts. But then there are a few Neo Banks for couples. So what do I know?
But for more information on Neo Banks for couples you may look here - Spouse joint account