That's a great point!
For me it's a combination of two.
Personal validation - "can I build something people love?"
And financial - "can I build a successful company around it?"
So this way there is no event after which the project becomes less relevant for me. It's a process, and I expect it to be along process.
That's the reason I can't commit to open-sourcing my product at some point in time.
However at the same time there are pretty successful companies that have a trust of being "secure and privacy first":
- Apple
- Telegram
While at the same time there are pretty good counter examples:
- PostHog
- Signal