Earlier quoted context omitted.
It's no longer a common everyday saying because it's become synonymous with the sinister sexist undertones that it implies. It's like asking someone to "Netflix and Chill" today vs 3 years ago. At some point it may not have only meant one thing but those days have passed.
Says who? You and a few others? Lots of people disagree so maybe you are in a tough shit scenario here. Unless you actually have got someone fired for an innocuous comment. Then it's tough shit for them, I suppose.
Google "telling women to smile" (no quotes) should prove enlightening. If you want something more specific, I've provided two references in the post below.