I disagree with Geo8rge. Folding bikes aren't used in competition because they are not allowed in competition. If cycling associations allowed recumbants and odd shaped bikes, races would be much faster.

Some folders are at least as fast as road bikes, and at least one upright speed record was set on one.

In fact, road bikes are one of the less efficient bike designs out there, but they are the standard, and cycling associations don't permit anything that weighs too little or looks too weird to ensure that it's all about the rider and not about the bike.