why are so many women in London changing their lips?

 In the last 3 days in London, as I wander around on foot, on bus and on the tube, I have come across at least 5 women who have changed the shape of their lips. I am wondering if this is a fashion in London? 

I have not come across this large number of women who have altered their  lips in Toronto, Canada  where I live. 

Just curious.