They're stylish, I'll give it that.
But...........
They're made of taffeta, which is not the easiest-wearing material in the world. It tends to be hot, easily wrinkled, dry clean only, stains easily, and is quite stiff with no 'give'. Fine for formal wear, not so appropriate for uniforms that one has to wear for 12 hours everyday.
That dress appears to be rather low-cut. Again, fine for formal wear, but might give passengers more of a view than some passengers really want. (As stated above, keeping in mind that a great majority of F/As don't moonlight as runway models.)
Most F/As aren't 6'0" with no figure. I howl with laughter to picture myself in that uniform right now, I wonder what their 'maternity' version looks like!