To give an intuitive explanation of why planets and their moons might end up facing each other - imagine a pair of dance partners, holding each other tight. The tighter the hold, as they spin around each other, the more likely they are to keep facing each other. If the weaker partner can't hold very tightly, the stronger partner has the freedom to swivel around, while his partner has to keep facing him, in his steely grip.
That's right, the Earth is sexist.