Snail-mail is in trouble in most parts of the developed world, because online services have replaced so many processes that were running on paper.
Providing an example from my country and neighbours, i.e. the Nordics. Look at the graph that has numbers of delivered letters in different countries - it has roughly halved in 10 years, and the trend continues:
https://yle.fi/uutiset/3-11236284
Parcel deliveries are growing, but there the postal services have competition.
As the volume of letters decreases - particularly in businesses and offices but also in private lives - it becomes increasingly difficult to run the service without financial loss.