Why doesn't the Earth's distance from the sun cause the seasons?
The eccentricity of the Earth's orbit is about 0.0167 which makes the orbit nearly circular.
The Earth is at perihelion, its closest distance to the Sun, around 3 January which is in the Northern Hemisphere Winter. Likewise Earth is at aphelion, the furthest distance from the Sun, in early July which is in the Northern Hemisphere Summer. Clearly the distance from the Sun doesn't affect the seasons significantly.
The Earth's obliquity, or axial tilt, is the main cause of seasons.