I totally agree with you, handwritten notes have a power that is often underestimated in current marketing. Precisely because we live in such a digitalized era, where everything is automated and massive, a gesture as personal as a handwritten note highlights much more and generates a strong emotional impact. It is not just about thanking or giving greetings, but about demonstrating that someone behind the business really took the time to write something unique. This authenticity is difficult to replicate with an email or an automated message.
I have seen specific cases in which small brands, such as online stores of handmade products, include a brief note written in each package. Something as simple as "Thank you for your purchase, I hope you enjoy this product" accompanied by the person's name, you can make a difference in customer experience. Many times, that detail ends up being shared in social networks, which amplifies the visibility of the brand at no additional cost.