Question

Why don't the Sun's rays fall perpendicular at all the places of the earth

Answer 1

Sun rays fall perpendicular to another way which is in the form of the earth axis which is parallel to itself at every time.

Even, the obtuse angle and also always going to have the first-class support and solution.

On the other hand, the earth has sounded in the round format and sun never to right above the poles.

Answer 2

Just because of the inclined angle and spherical structure of the earth.  

The region between Tropic of Cancer and Capricorn is the only place that experiences the sun rays vertically overhead at some particular time. As already known, the earth is revolving around the sun at a angle of 23 degree inclined to the plane of the orbit.