In real life, some parts of an object are heavier than others, causing the object to rotate while falling or move slightly. But in Blender, it just falls perpendicularly till it reaches a surface. Is there a way to make an object fall in a more realistic way in Blender?
In real life, falling objects don't rotate much. It is a common misconception that heavier are more affected by gravity. But really, all objects (or all parts of objects, in this case) experience the exact same gravitational force no matter how much they weigh.
Occasionally, for objects that are light enough air resistance matters a lot, or fall long enough small changes have a large effect, or fall so fast air resistance is the main limiter of their speed, air resistance may cause some rotation. This is because air resistance disproportionally affects light objects and objects with greater area or speed.
In these cases, blender would be missing some rotation that occurs in real life, since blender doesn't simulate air resistance.
But these are unusual scenarios. Once you look at more normal objects, like a pen or a ball, air resistance becomes negligible and no rotation occurs.
There may sometimes be a spin on falling objects if you drop them imperfectly by hand, and accidentally spin them as you are dropping them. And objects that fall off a ledge rotate because the side still in contact with the ledge is pushed up by it. Most of the time, if you see an object spinning as it falls, one of those two reasons is why.
If you want to simulate that sort of effect, as if your object was dropped by hand or rolled off something, you can add it in manually, as others have said.