There are different probabilities for everything. If there's clearly a one in ten chance for something happening, obviously you wouldn't roll a six-sided die. You'd roll a ten-sided die. It's useful to have all kinds of sizes of dice when you play. You never know when you might need it. A ten or twenty sided die is useful in deciding how many storm troopers are waiting for your players in a room. You could also use a six-sided die for this for smaller totals or roll two using one for the tens digit and the other for the ones digit.

You can also assign to certain instances, events, or weapons some sort of probability for something happening. I once played with a relic that had a ten-sided die assigned to it with difficulty levels set for certain things you tried to do with it. I have also used what I called an "anger die". It was a ten-sided die that the player would roll when the GM said to (when the player was getting really aggravated). The player would keep an "anger total" and when the player hit 30, he/she/it would get really mad and act upon it. There are several other uses for larger and fewer sided dice. Discover some for yourself.