Social activity comes in a distant third to eating and resting for foraging animals. When more time must be spent foraging, animals are more likely to sacrifice time spent on aggressive behavior than time spent resting. Extremely efficient predators have more free time and thus often appear more lazy than relatively inept predators that have little free time.
Many animals who live in groups also use baby-sitters. Some might consider that lazy but it does give the parent a chance to feed, groom and rest. Just like us, if one cannot have the basics in life coupled with a bit of relaxing we can burn out which can make our immune systems weak.