Doesn't anyone who walks into a shop more than once 'know' the staff? I recognised repeat customers when I worked in retail, even though I didn't know their nam

Doesn't anyone who walks into a shop more than once 'know' the staff? I recognised repeat customers when I worked in retail, even though I didn't know their names, and customised my service to them (e.g "how's the XXX you bought last time?"). That's illegal in Germany?