Two reasons in my mind. A lot of the media establishment grew up in the RS era of winning so are either fans or have a soft spot for them and a natural dislike for us.
The second reason is that we are usually the team who stop the formation of their beloved super six. When we were rubbish pre Moyes, or under Martinez they were more than happy to big us up. When we threaten the top end of the league showing up certain clubs who spent more than us, taking European spots from others, they don't like it.