every child is different. Mine are 6 and 7, last year we averaged 10-12 miles a day. that's a lot of walking, so i can see how an 8 year old could use one every now and then.
We rented a double stroller last year, and it got used. Both kids walked a lot also, but at times with the heat and the distances, why bother fighting them?
Maybe I'm just to far removed from having small children (my son is 23 now). But when I think of a stroller I think of a baby, not a child in grade 3 or 4.