The only manufacturer I am aware of using water injection is BMW on one (or some) of their M Sport models. They source the water from the air-con condensate. I think one reason water injection is shunned is that it would require an anti-freeze additive in cold climates and they don't want their customers having to mix it or handle it if it is methanol. I am just guessing on that though. Maybe if the emission tests were conducted at high loads the fuel cooling would end but as the testing is done at very low loads, the manufacturers can do what they want outwith the test regime - and leave the end user with the fuel bill (and diluted engine oil). Rowing back on the fuel cooling could force them to lower CRs and lose economy across the board. Fuel cooling though is one reason why the downsized turbo engines don't always deliver the expected fuel economy gains in real life running.