Why isn't it used in F1?
In World Touring Cars it is used alot in Qualifying.
In F1 I very rarely see the cars running anywhere near each other, they always set-up more for free-air driving. Surely it would be of greater use to the teams to run cars behind another, at least in Practice to see how they would behave.
Also in Qualifying, I could see it be of use to a team, say Renault, where one driver is clearly faster than the other, to use the slower car to provide some sort of tow over the start/finish to give an extra boost to the opening sector.
Does the con simply out-weigh the con in this instance? Getting into said tow, around the provider simply too much of a detriment to the teams. Or would this be classed as team-rules.