Economists keep track of the number of "unbanked" people. At the lower end of the spectrum the % of "unbanked" individuals is quite high and they live almost exclusively in an all-cash economy. Particularly in immigrant communities. There are a number of problems with being "unbanked", in particular if your house is burglarized you can lose your entire life savings, and you have little to no access to formal credit, which in the US at least, is the primary path to accruing wealth or at least savings.