I guess it comes down to the selling of advertising space for those televised replays. Each of the 4 clubs have far more attraction than MK Dons, and I guess that the TV audience will therefore be bigger.
There’s no great surprises in the choice of 4th round ties, with the exception of Arsenal v Coventry. That said, with the exception of the ties listed above, there isn’t much in the draw for the media to drool over, with many premier league clubs drawn at home to lower league opposition.