Why is it that fast athletes only hold the seat while running with their bikes?
Anyone who holds their bike by the handlebars while running is automatically slow. 
Discuss.
Simple, whe you hold from the handlebars you can not put a distance between you and the bike. pedals and mid section of the bike gets in your way of your stride. Hold from the saddle (not the seatpost!) and you will have a decent distance between you and the bike (mostly the the drivetrain) When you run keep the bike always infront (push) if you do it from the handlebars, you will be pulling the bike.
Try it and you’ll see.
I carry my bike from top tube. Otherwise all the bouncing around in transition tends to jar stuff loose worse than if I hit bumps during the ride. My 2 cents. Plus it seems that every tri I’ve been in this year has had 2 inches of water on the ground due to heavy rains so it’s harder to do the seat-hold run thing.
i agree with swimfan. amazes me to see people in transition running with BOTH hands on the handlebars.
it takes a little practice to get the steering down, but holding the seat is def the best (and fastest) was to run with the bike.
Simple - bikes are steered from the saddle, not the bars. Despite how most people ride them - which explains their fine bike handling skills…