because Poch is with spurs and Spurs have always come thru for United or until recently.. the pecking order argument... Rafa's outside of that really.. with Poch, they can emulate Tottenham's way and unlimitedly became more successful as they got more walla
Or the constant linking of him to Utd in the media has meant loads of people keep putting money on Poch so the bookies have shortened the odds to make it less attractive to bet on him. They need people to bet on other managers
If he keeps doing well then they'd be foolish not to keep him. Guy clearly loves the club, understands completely the kind of football their fans want to see and has the ear of their greatest ever manager to call on if he ever needs pointers.