> everyone from political campaigns to the local deli, will start doing the same

It is definitely a matter of time until this stops working. From a quick google of "handwritten letters" here's what I got:

• https://www.handwrytten.com/

• https://www.scribeless.co/

• https://roboquill.io/

• https://handwrittenmail.com/

• https://letterfriend.com/