Recently several comanies such as Adidas, Skins, etc. have touted the supposed advantages of compression tights. They claim that wearing them will increase power output due to reduced muscle vibration, assist in the flushing of lactic acid through increased circulation and assisting venous return of blood upwards and out of the legs, as well as claiming to reduce oxygen costs of a given pace. Most extraordinarily they claim to substantially (Skins claims 33%) increase time to exhaustion at a certain output.
If this is all true why aren't more elite mid-d and distance runners wearing them? Are there downsides that outweigh these advantages?
Serious replies only please.