It's the same concept though. Getting the front of your body ahead of your feet allows a part of your body to cross the "finish line" faster. The same concept can apply in baseball. With a correct slide, minimizing the distance that you actually slide...you can get to first faster than running through it. However, whenever your feet are not on the ground pushing forward, your body is decelerating. If there were a way to lean foward and touch the base without losing your running power in the process, I'd agree completely. The only time I would ever advocate sliding into first would be to avoid a tag. In any other situation it's just not worth it, both from the injuries that can result and from the necessary deceleration to position your body to dive at the base. Sure, theoretically, it may be possible to not purposely decelerate to dive, but in practice that doesn't happen.