I'm 29, and think I look my age. I think this because I don't get ID'd when buying razors or medication (I don't drink, smoke or go clubbing so have never had to have my ID checked for anything else lol). Also because if I mention that I'm at university people seem surprised until I mention I'm retraining.
However, today I went shopping alone and noticed how I felt like I was being talked to like I was young/a child. For example, I was in Sally's and know exactly what I was looking for so headed straight there. The cashier said 'hello darling, do you need any help?', she was probably around my age which I wouldn't expect for her to call me 'darling'. Then I was in Boots paying on the self-service checkout and struggled to scan an item for probably 10 seconds before the lady came over and said something like 'here sweetie, let me help you. There you are, sweetheart'. The same sort of thing happened in a third shop.
It's not necessarily the pet names said in these examples, but more the way it was said. It's the way I would speak to a child. I am more of a reserved/quiet kind of person so I wonder if I'm somehow projecting some kind of childlike-ness?