Joel Jamieson put up an excellent article on his website, 8 Weeks Out, called Conditioning for Strength Athletes.
Basically, what conditioning is useful and effective for athletes whose sport involves demonstrating strength - think of sports like strongman, powerlifting, Olympic weightlifting.
But it has an excellent point about longevity and conditioning, all people in all walks of life:
"Let’s look at what the research has to say about whether or not conditioning is all that important:
A number of prospective studies have demonstrated that VO2max, which is directly related to aerobic fitness, is the most important predictor all-cause mortality.
Research conducted by Johnathan Myers showed that study participants who were categorized as having the lowest VO2max value were 4.5 times more likely to die from anything, particularly cardiovascular disease, than those with the highest VO2max levels (Myers, 2003).
Another article reviewing 11 different studies showed that regular physical activity increased life expectancy anywhere from 0.4-4.2 years, but aerobic endurance athletes showed an increased life expectancy of 4.3-8.0 years (Reimers et al, 2012)."
So regular activity is +0.4 to +4.2 years on your lifespan. Training for aerobic endurance is +4.3 to +8.0 years. That's a tenfold increase in the base, and nearly double the top end.
And before that, "the lowest VO2Max value" is associated with being 4.5 times higher mortality from all causes.
Train for cardiovascular endurance, gain lifespan.
It doesn't only do that. Cardio training can improve recovery between workouts, increase recovery during workouts, and give you overall increased work capacity. In other words, get better faster, get more from your rest between sets, and get more done period.
That's what cardio is good for.