It also misses the other rather obvious factor: newspapers have owners, editors and readers. Owners often are very open about their agenda, editors have owners

It also misses the other rather obvious factor: newspapers have owners, editors and readers. Owners often are very open about their agenda, editors have owners to please, historic reputations to uphold and their own politics (which is often a bit more firmly established than a twentysomething first jobber's) and the subset of the population that actually pays for newspapers has their own opinion of the sort of content it wants to read. Most of the stereotypes about bubbles of young underpaid, overeducated middle class status-chasers living in the capital and associating mostly with other young people, journalists and politicos/intellectuals could be applied to the UK, but our mainstream print media leans right (with a couple of very outspoken exceptions, whose journalists live in the same bubble!), as you might expect from the personal politics of their owners, and newspapers are bought in much greater numbers by older, more right wing people