Eggs are egg-shaped for several reasons. First, it enables them to fit more snugly together in the nest, with smaller air spaces between them. This reduces heat loss and allows best use of the nest space.
Second, if the eggs roll, it will roll in a circular path around the pointed end. This will reduce the danger of the egg rolling out of the nest. Moreover le strongest shape would be a sphere, but spherical eggs will roll away, and this will be unfortunate, for birds that nest on cliffs.
Most eggs will roll in a curved path, coming to rest with the sharper end pointing uphill.
There is in fact a noticeable tendency for the eggs of cliff-nesting birds to deviate more from the spherical, and thus roll in a tighter arc.
Third, an egg shape is more comfortable for the bird while it is lying, rather than a sphere or a cylinder. Other shapes have structurally weak points and edges. Finally, another important reason is that hen’s eggs are the ideal shape for fitting into egg cups and egg holders on the fridge door. No other shape would do.