Calling with the nuts

[LondonBroil]

Online 1/2, fairly loose passive. Not a whole lot of pre-flop raising.

On 2 seperate hands I witnessed the same guy just call on the river when he was holding the nuts and he was closing the action.

First hand hero has A [img]/forums/images/icons/club.gif[/img] 5 [img]/forums/images/icons/club.gif[/img] on a board that read Q [img]/forums/images/icons/club.gif[/img] J [img]/forums/images/icons/club.gif[/img] 4 [img]/forums/images/icons/heart.gif[/img] 2 [img]/forums/images/icons/diamond.gif[/img] 6 [img]/forums/images/icons/club.gif[/img] . There were 3 people at the river, first one bets, second guy calls, and our hero only calls.

Second hand our hero has Q [img]/forums/images/icons/diamond.gif[/img] J [img]/forums/images/icons/heart.gif[/img] with a board of J [img]/forums/images/icons/spade.gif[/img] 10 [img]/forums/images/icons/spade.gif[/img] Q [img]/forums/images/icons/heart.gif[/img] Q [img]/forums/images/icons/club.gif[/img] 9 [img]/forums/images/icons/diamond.gif[/img] . This time it's only him and 1 opponent. Opponent bets, hero only calls. (opponent had AK)

Is there some kind of benefit to only calling in these situations that I'm not aware of?