Small kids usually can't ride in real go-karts, but because these go so slow and on a rail they let little kids ride. This is many children's first time driving anything... and it creates memories.
In fact, many parents are taking their kids to Disney now because they want their kids' first memory of driving a car to be just like their own experience. It's a cycle. And Disney likes to milk money from nostalgia. So it ain't goin' nowhere.