Explain why there is no higher latitude other than 90 degrees north and south

A full circle is 360 degrees, but latitude only covers 1/2 of a circle, from the North Pole to the South Pole, which would be 180 degrees.

The mid point of latitude is the equator, which is the Zero axis, so latitude goes 90 degrees North and 90 degrees South.

90 + 90 = 180