Fork crown mounted handlebars are usually on track bikes because the brake gets in the way, and you have to do something like mounting the brake on the rear of the fork which severely limits the amount you can turn the handlebar. Solutions like ergostems can introduce a noticeable amount of flex. One might be able to argue for a low-pro funny bike frame with a negative rise track stem if it can get low enough or just regular drops, but this starts to lose novelty factor. Most of this became obsolete with the introduction of aerobars.