A newly planted tree might look more or less identical to a wild sapling, but it differs in one key respect. Until the root system of the planted tree expands, your new tree has almost no real mechanical connection to the soil matrix around it. You can, as you are probably aware, tip it over with a good shove. And so can the wind.
This is the major reason for staking newly planted trees, and it is advisable to keep trees staked for 1-2 years. Roots grow relatively fast, but they don't achieve a solid bond until they have gotten fairly thick. A tree that gets blown over after a year is doubly injured, because you have injured the new roots as well as the branches.
There are better and worse ways to stake a tree, however, and a bad staking job is often worse than nothing.
First, the stakes themselves are often a weak point. There is nothing magical about the act of hammering a stake into the ground. If the ground is wet clay, and the stake is less than 12" or so long, you might as well be connecting the cordage to the ground with scotch tape. Use stakes heavy enough for your soil and your job.
Second, the point of the stakes and cordage is not to hold the tree upright. If your tree is not upright to begin with, it has been planted improperly. If a tree has slouched over somewhat, it is possible to adjust this by putting traction on it from the opposite side, though this is a little risky, for reasons we will discuss in a moment. But it is foolish to place newly planted trees under tension. This can actually assist the wind in toppling a tree that would have stayed upright if it were not staked at all.
Third, the contact point between your cordage and the tree is a vector for damaging the tree's bark, and then the cambium layer. Tight, bare wire or rope is the worst option. You can use a loop of garden hose as a cushion, or shell out big money for commercial products that do the same thing. But in fact you want to minimize any type of friction or pressure between the tree and the cordage. If you need to place the tree under traction, you can't avoid this, but in many circumstances you can.
The best practice, then, is to use tall stakes, and run your cordage between them, tightly, with a loose loop of cordage around the trunk. So when the wind gets serious, the tree is protected, and the rest of the time, the bark is protected.