Executives also want to take the rolodex with them, hence they have an incentive to keep a personal CRM so that they keep their contacts after they leave.
Superhuman sold to executives for $30/month - which is a relevant (high) price point.
I'm not entirely sure what the first point has to do with the second - can you help me understand what Superhuman has to do with anything? It's just a gmail client at the end of the day, isn't it?
My understanding is people who want to keep their contacts have 1) a lot of them in the actual inbox 2) have their Linkedin to fall back on 3) can always fall back to exporting all their contacts when they leave.
Apropos of nothing, $30/month/user is roughly the base price of Salesforce, and they have 3 more tiers significantly above that. High for a consumer, but pretty cheap for professional tools, and they don't sell licenses one at a time.
So for a personal CRM to work, you'd need to sort out, at minimum, the monetization piece and the data fidelity piece. If you open source it, you still need to make sure people keep the data up to date and that's actually pretty hard.