Because no one says no to Henry Bolingbroke

Only the strength of his father's friendship with Bolingbroke has him here -- that and Kate's insistence that he must occasionally act like he is part of a company, with responsibilities to allegiances greater than his own. This is why he is glumly walking up this long driveway with a bottle of good scotch under his arm, though he neither cares much for whiskey nor for the man in whom most of it will inevitably end up.

"I have far better things I could be doing with myself tonight," he mutters, when there is still time to make a phone call and go home to those pastimes, like building a model airplane or butchering some karaoke or, God save them all, babysitting.