RPGMemes

Imagine you roll 3d6. There's exactly one way to roll a 3. You need all three of those dice to come up 1. But there are many ways to roll a ten. [{1,3,6}, {1,4,5}, {2,2,6} ...etc]. You're more likely to get totals in the middle of the range. If you rolled 3d6 many times and charted the outcomes, it would look like a bell curve. Most of the results are in the middle, with fewer results of the outliers like 3 and 18.

If you roll 1d20 many times and chart the results, it's a flat line. You're just as likely to get one number as any other.

Go play around with https://anydice.com/program/e6 if you like.

I personally find the flat probability of 1d20 unsatisfying. I prefer when the average, most expected result comes up more often.

Like imagine you're throwing darts at a dart board. You probably don't have an equal number of darts on the floor as in the bullseye, and also an equal amount in between. They're probably mostly clustered, with some outliers.