"Try and explain to the average user why URLs on HN look like this"
You're missing the point, you don't have to understand that anymore than you have to understand why my street number is 4 digits long or my street name ends in "street" instead of avenue, crescent, drive, lane, etc.
You're missing the point, you don't have to understand that anymore than you have to understand why my street number is 4 digits long or my street name ends in "street" instead of avenue, crescent, drive, lane, etc.