The favor done professionally includes the details you would handle for a paying client.

Unpaid work invites a quiet reduction in care. The tidy edges, the follow-up, the clear explanation of what was done: these get trimmed because nobody is paying for them, and the friend receives a version they cannot really complain about. That gap costs more than the time saved, because they now have a half-finished thing and no standing to mention it.

If you are doing something for free, decide the standard before you start and hold to it. Better to offer less scope at full care than the whole job done casually.