The studios like people to be able to refer to their films in a 'hip' and 'catchy' manner- started with Terminator 2 (aka T2), resulting in X-Men 2 being called 'X2', and amusingly the studio trying it with 'League of Extraordinary Gentlemen' by thinking people would call it 'LXG' (obviously they couldn't spell or thought calling it 'LEG' would just be silly... lol)
