Why unable to? To read the blockchain you use any Ethereum RPC provider, pure HTTP interface no need for MetaMask.

Embedded browsers and iOS safari do sign transactions using WalletConnect. Or you can deeplink into a wallet dapp browser too.

Oh nice, I didn't know about that. How does it work? You sign into a centralized wallet provider like paypal?

For most things my gut says deeplinking to a dapp is going to kill conversion. Use cases I'm thinking are selling audio samples or a sewing pattern... stuff people use gumroad for.

I wonder how the transaction costs compare at these price points ($1-20). Hoping that's gotten better. Last time I tried sending eth it only made sense for big transactions.