I'd argue that at least some yogurt is a prebiotic in that it's fermented, contains a community of lactic acid bacteria and hasn't been pasteurized post fermentation (although in the US it's typically made with pasteurized milk). For instance the stuff I eat is labeled to contain L.bulgaricus, S.thermophilus, L.acidophilus, Bifodobacterium, L.paracasei, and L.rhamnosus.
But it's kind of an outlier in the yogurts you can buy in the supermarket.
No idea if any of that bacteria makes it past the acids in my stomach. For me it's more about the taste - and that the cows were allowed to browse on pasture.