In addition to higher CG, greater weight and greater drag, a taller chassis can provide greater rigidity. And if a car generating 6 Gs lateral acceleration isn't exceedingly rigid, keeping the inside wheels planted could be dodgy.
The extreme example of a low chassis would be just flat a sheet, which obviously would have low rigidity. This also is why convertibles often are heavier than their coupe counterpart -- material was added to the frame to replace the loss of structural rigidity when the roof was removed. The ultimate question for an F1 chassis is how high equals
adequate rigidity. Macca have had a differing answer to that question the past few seasons than the rest of the field.
When I first saw the new RB8's letterbox intake on the nose, I laughingly suggested it was a bit of misdirection. Last week I found this photo on a Polish F1 fan's blog which I check from time to time because he gets insider information on the progress of Robert Kubica's recovery.
The RB8 also has an air intake
under the nose. This was posted nearly two weeks ago but I've not seen it remarked to in the English speaking motoring press. I've lost track of it for the moment but there was another photo with the nose removed showing where the channel passed beneath the aluminium bulkhead at the foot of the survival cell, so it definitely extends at least as far as the cockpit.