A look at the Earth from space, the North American continent is fully visible, but the South American continent follows the curve of the Earth around to the other side. Also note the left side is darker as the Earth rotates into darkness.

Question. If Earth was flat where are the other continents hiding? Why isn’t the whole planet in full sunshine? Why is the shadow the Earth casts on the moon always round? (which gives us the moons phases). If Earth was flat the shadow would sometimes be a line. Why is every planet a sphere but not Earth?

Occam’s razor says that usually the simplest explanation is the truth.

From Wikipedia :

In philosophy, Occam’s razor (also spelled Ockham’s razor or Ocham’s razor; Latin: novacula Occami) is the problem-solving principle that recommends searching for explanations constructed with the smallest possible set of elements. It is also known as the principle of parsimony or the law of parsimony (Latin: lex parsimoniae). Attributed to William of Ockham, a 14th-century English philosopher and theologian, it is frequently cited as Entia non sunt multiplicanda praeter necessitatem, which translates as “Entities must not be multiplied beyond necessity”,^[1][2] although Occam never used these exact words. Popularly, the principle is sometimes inaccurately^[3] paraphrased as “The simplest explanation is usually the best one.”^[4]