A late yes can become less useful than an early no.

Delay is often mistaken for kindness. Holding off on a refusal feels gentler than delivering it, and meanwhile the other person is keeping a space open, turning down alternatives, and building around an answer they do not have. By the time the yes arrives, the moment it would have helped has gone, and the goodwill was spent on waiting rather than on the thing itself.

Answer the request you have been avoiding. Even a clear no this afternoon gives somebody back their week, which is worth more to them than a reluctant agreement next Friday.