I'm going to share the tips and tricks that the pro's use to keep you from getting bored before the first verse is over. This means the lack of those minute differences makes even the world's most unique and complex drum pattern boring after 30 seconds. The problem is that the human ear and brain can distinguish very minute differences in sound. And how many real life snares trigger more than one sound each time it's hit? That's the least realistic thing ever. It'll be the exact same hits over and over again and no drummer hits the hi-hat at the same perfect timing at the same spot on the hat with the same force a million times in a single song.
Using samples of real live drums only helps to a degree. Knowing how a real drummer swings his sticks tells you nothing of how to transport that magic into the computer.
There's a ton of advice out there being spewed every time someone asks 'How do I program realistic drums?' 'Drum programming isn't hard, dummy,' they say.