[AndyJudge]

I suspect because some of the target market would be put off by having the beast unleased.

I know my 2015MY XC60 D5 in sport mode is mighty responsive without any noticeable change in Mpg. In fact on a motorway run it seems to use less maybe because the engine is kept in the optimum power band for longer.

I do notice that sometimes using it around town it can potentially catch you unawares.