Because of the negative connotations attached to the word, which are due to a long-running propaganda campaign, financed by the Western corporate elite, which aims to convince everyone that letting the government provide services, support the population and actively work to improve quality of life for all is a one-way ticket to authoritarianism and misery, but letting the mega-corporations do whatever they please and leaving the poor and oppressed masses to fend for themselves is somehow going to make everyone better off.
Obviously, we all know this is not true, because the most economically left (that is, socialist) countries in the developed world (e.g. Scandinavia) have the highest standards of living, while the USA lives in a socio-economic apartheid, riddled with violent crime and hopelessness.
But hey, as a media channel, it’s conservative, it’s American, and it’s Murdoch;
considering their intentions and the probable target audience, it’s not like it actually has to make sense