Because most of the media are in the pockets of the Tories. Private Eye are not.
A significant amount of stories that look bad for the Tories are muted by major news outlets (BBC, ITV, Sun, Daily Mail, Telegraph, Times) in exchange for favours for their owners, preferential access on the Tories' terms, or to just to ensure that the Tories stay in power because the owners are Tory party donors and have a vested interest in their party being in power.