Urban Permaculture system pond? Why?

I live on an urban lot of about 1/2 acre in zone 7a and have been designing a food forest. I’ve seen people in similar situations include small ponds but I don’t really understand the why. Space is limited…is using it for a pond worthwhile? It wouldn’t be big enough for eatin’ fish. I may be skeptical because of my dearest partner’s expensive, failed stock tank pool project. 😅