Just one - Summilux pre-aspherical 35mm (= 50 m on my Leica M8)
You didn't take account of those of us who only own a crop-factor camera! 😀
Since I only have one camera, I only need one normal-view lens, same as I have one wide angle (25mm), one short telephoto (50mm Summilux pre-asph), and one long telephoto (90mm).
Personally, I choose the lenses I like carefully (to end up with the Summilux 50mm (which I'm definitely staying with - a perfect lens), I tried and sold an Elmar 50/2.8, Jupiter 8, Canon 50/1.2 and a Summicron): once I've done that, I prefer to concentrate on the image and leave lenses out of the equation (bar focal length).
I like to predict how my equipment behaves under any circumstances, hence the reason why I only own one camera and four lenses. (Perversely, although I use a rangefinder, I mostly take still lifes and hate street photography - the M8 works well as a studio camera once you've learnt its foibles!)