Here's why:
* Shape (Conformal): Maps that preserve shape are called conformal maps. They accurately represent angles and the relative shapes of features, but they may distort distances and areas. Examples include the Mercator projection.
* Size (Equal-Area): Maps that preserve area are called equal-area maps. They accurately represent the relative sizes of features, but they may distort shapes. Examples include the Gall-Peters projection.
So, what's the solution?
The best map for a particular purpose depends on what you're trying to show.
* If you need to accurately represent shapes, like for navigation, a conformal map is best.
* If you need to accurately represent areas, like for comparing the size of countries, an equal-area map is best.
Compromise projections: Some map projections aim to minimize distortion in both shape and size. These compromise projections, like the Robinson projection, are often used for general-purpose maps. However, they will always have some degree of distortion.