How does Worldcoin plan to solve for people in wealthier countries not wanting to scan their eyeballs (because the UBI isn't meaningful enough)?

Likely through a long tail of value props beyond the financial incentive 

For example, apps that require proof of personhood to use them, or voting schemes that require you to verify as a unique human 

Also early adoption of new technology often happens in developed countries b/c it is seen as high status

Building /bright-moments - minting onchain art IRL | /purple #15 | FID 129 #magikarp

Rome, Metropolitan City of Rome Capital, Italy

What historical technology have been adopted in developing countries and then become the norm and high status in developed countries?

Chasing Curiosity. Empathetic Accelerationist. Founding Fullstack Engineer @icebreaker. YC S16, KB7. 
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Real World Ethereum 🌎 
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My original point still stands. 

WhatsApp use is low in the US compared to iMessage. WhatsApp is popular for people communicating internationally.

What’s the equivalent for worldcoin?

Built in Silicon Valley , adopted in the developing world first and eventually everywhere is exactly what Worldcoin is going for, right?

(Not saying I agree w Worldcoin but you asked for a successful example of bottom-up adoption and I think WhatsApp qualifies)