Do you carry out any online shopping(Amazon,Ryanair,etc) , make use of supermarket loyalty cards or heck even carry out google searches.
There is a more tracked information about you personally and what makes you tick than what the banks have about the stores where you spend your money each month.
I'm sure they carry out analysis of what people do with their money but it's going to be at larger macro level.
As you say the bank even if they could tell have no interest in how many Jaffa cakes you are buying but maybe where you buy and method of payment is important at some aggregate level.