Google's .app TLD ships with mandatory HTTPS at the registry level — perfect trust-positioning for consumer-facing Bitcoin apps (wallets, sparplan, paying). The TLD signals "mobile-first product" to retail audiences.
.app enforces HTTPS at the registry level, so every site under it is served over an encrypted connection by default. For a Bitcoin wallet or payment app that is a meaningful signal rather than a technical footnote.
The extension also sets an expectation. A visitor arriving at a .app expects a product, not a brochure — which makes it a poor fit for a corporate site and a good one for the thing people actually download.