I'm late to the party, but it's certainly due to chance. Earth's current rotation rate is much slower than it used to be. It's estimated to had been around 21 hours during golden age of dinosaurs (around 100 million years ago), and some estimate the rotation may had been as quick as 10-12 hours when Earth formed. So, what's slowed it down? The moon. Our moon is relatively large, compared to the parent body, and it exerts a gravitational force on us, slowing out rotation. Every year, the rotation does decrease, while at the same time, the moon's distance from Earth increases (less than a couple inches a year or so). So, the rotational period will continue to increase as time goes on, but the rate at which it does so will be less. The 2 moons of Mars are likely captured asteroids and are far smaller than the parent body, and so their gravitational influence on Mars is negligible in comparison.
