So once everybody has automated this, the next level will be the handwritten note with a personal detail, which will increase (repeat) sales.
Back in the day, I used to write a handwritten note with every single box I sent out. Since I had often had a conversation with the customer prior to that, I could often include some personal detail, showing that the message was not generic but truly written for that person. (I did have a generic message that I would use in a minority of cases.)
It does take a little bit of dedication and love of the customer to do this over and over again, so I'm not convinced shady, unscrupulous marketers would do it.
That depends on if they are handwritten, or some font that looks sort of like handwritten. At least until/unless AI can write thank yous that pass the Turing test. Right now the effort vs reward of a thank you is not worth it for most sales, and people can pick out computer generated thank yous.
Even then, Wal*Mart will never send you a thank you note - the cost of postage alone is too high. However car salesmen have long ago figured out it is worth writing a thank you - it only takes a few repeat customers to make the time and postage worth it.
That said, if you are a small business a handwritten thank you is good advice. Very few small business run a many customers with a low profit business model (only retail), and as such you are probably in one area where a handwritten thank you will help.
Back in the day, I used to write a handwritten note with every single box I sent out. Since I had often had a conversation with the customer prior to that, I could often include some personal detail, showing that the message was not generic but truly written for that person. (I did have a generic message that I would use in a minority of cases.)
It does take a little bit of dedication and love of the customer to do this over and over again, so I'm not convinced shady, unscrupulous marketers would do it.
Caveat: My business eventually failed, so...