Back to the nature eh!!!
I remember when I was in school, due to financial reasons, I won't have any sports shoes, so I'd alway play barefeet, it used to be fine, except for small stones/thorns sometimes popping out of nowhere and in the sole.
If you run barefoot on the ground that's not concritised (difficult in HK though), it really is better for two reasons -
1. you don't get tired that fast as the feet doesnt hit a hard surface, so its easy on the legs overall
2. Due to tiny land particles/stones, you get accupressure massage.