Of course it's useful, that's why function modifiers like 'const' or 'virtual' (thinking from a C++ perspective) are widely seen as useful, but making one function virtual doesn't force you to propagate that all the way up the call tree.
Constness is infectious down the stack (the callee of a const function must be const) while asyncness is infectious up the stack (the caller of an async function must be async). So you can gradually add constness to subsections of a codebase while refactoring, only touching those local parts of the codebase. As opposed to async, where adding a single call to an async function requires you to touch all functions back up to main
