No "Sell-by date"

Pret, a cafe in London, sells only fresh sandwiches, putting a sign "No Sell-by date".  They don't use any preservation nor give you leftovers from the former days.  The rhetoric sounded quit interesting for me as an English language learner.  I just found out it is part of public relations carrying a symbolic message to the customers.  On the way back to the residence, I took a close look at the "Use-by date" of fruit juice at Marks-and-Spenser.