Because not everyone put the camera on a tripod at eye level of a person standing up.
Camera on tripod low on the ground, eg macro, landscape shots to get a angle vantage. Camera on tripod with horizontal arm out to get a better angle not possible physically, eg. over a cliff. Camera facing down on subject on a table, eg product shot, macro. Tripod elevated above eye or head level, eg, to shoot over other people's heads.
Do I need to go on? You have to understand that a tripod is used to add stability. Getting the perspective you want is a separate issue from a tripod. A flipout screen is made to help a shooter compose better without lying on the ground, bending down all the time.. etc.. Using a tripod have nothing to do with using a flipscreen whatsoever.
So why even release a flip out screen so flawed in execution. And, why are you raving so much about it when it is executed so badly to the point that it is handicapped. This is no rocket science as this has been done so nicely on Olympus and Panasonic or a long time now?