What does histogram mean: it counts the number of pixels as per pixel values. Binary number has only 0 and 1 pixel, lets have example there can be 500 zero pixels and 200 one pixels. If we draw the histogram plot, the hist blue (default) line bar plot may on the axis itself, please look carefully.
Or
You can use the histogram function, you can do many ways to change the color or width of the hist plot, so that it is easily visualized.
I=imbinarize(rgb2gray(imread('1.jpg')));
[counts,binLocations]=imhist(I,2);
figure, histogram(I);
