Ask HN: Stealth mode seems like a weakness; why would anyone?

I've noticed some start ups call themselves "stealth mode" and get to >20 engineers and keep it that way. I see a lot of reasons why stealth mode is bad and good.

Building in public:

  - tests your idea (+)
  - allows for feedback (+)
  - forces you to ship (+)
  - turns revenue into a usable metric (+)
  - opens you to copy-cats immediately (-)
  - opens you to incumbent challenges (-)
  - not doing well immediately can mean death (-)

On the other hand, building in private:

  - keeps your idea secret (+)
  - launch with more feature-complete offering (+)
  - sort-of exclusivity for investors (+)
  - no customers = no pressure and vision focused (+/-)
  - no iteration/testing of vision (-)
  - admits that existential threats are real (-)

I'm sure there are a lot more.. What are your thoughts?