The UK left the EU but kept one of Europe's most active retail Bitcoin markets, with crypto providers registered with the FCA. The .uk TLD is the modern English-market signal, replacing the older .co.uk pattern. UK-focused Bitcoin brands use it alongside their .com for local trust.
The United Kingdom is one of the largest Bitcoin markets in Europe and it sits outside the EU regulatory perimeter, which makes it a separate go-to-market rather than an extension of one.
.uk is the short form that has largely replaced .co.uk in new branding. For an international Bitcoin brand it is the defensive purchase that stops a UK operator from launching under a name the brand already uses everywhere else.