The author says several times that they also encourage other people (e.g: grandparents) to email their child, so that's one reason.
The act of drafting an email/letter is also emotionally distinct from appending to a text file. For example, in a text file, you are probably more likely to abbreviate your thoughts or omit pleasantries like "Dear son," / "Love, Dad." Each email is also timestamped in a way that's much more "provable" than text in your file, and also immune to edits after-the-fact.
The act of drafting an email/letter is also emotionally distinct from appending to a text file. For example, in a text file, you are probably more likely to abbreviate your thoughts or omit pleasantries like "Dear son," / "Love, Dad." Each email is also timestamped in a way that's much more "provable" than text in your file, and also immune to edits after-the-fact.