Customer discount cards

It seems that I cannot shop in any grocery store or drug store any longer without being asked if I have my discount card. To obtain one of their cards I must fill out an application in which I am revealing information that I do not wish for just anyone to have access to. I know that they use this info and the accompanying tacking number to do just that - to track my purchases. If I don't obtain one of their cards I am penalized from receiving a discount. Is it not an act of discrimination to not offer me this discount because I have refused to give them my home address, phone number, etc.? If these retailers have discounts to offer should they not be available to everyone card or not?