Because Caltex Guarantee that there is no ethanol in their fuel unless it is labelled E10 ect. If you put non ethanol fuel in your motorbike or boat or numerous other engines that cannot run on a ethanol blended fuel and the engine is damaged due to ethanol being blended in it. Sue them for damages.
Caltex on their own web site says that they are aware that some engines including some motorbike engines, chainsaws, vehicles ect cannot use ethanol blended fuel. Hence they label their bowsers. Don't take my word for it, look it up.