The NHL is trying to build its brand, grow its market share, call it what you will. Olympics is a wonderful showcase for them, people tune into all kinds of sports they don't normally view. But the team owners for the most part view it as two weeks of injury risk to key players with zero return to them. So the league decides on their own version, a scaled down international tournament where they share the revenues and (mostly) control the messaging. They still got the injuries, but there's at least some compensation.
Personally, I think the NHL should continue to promote the sport of hockey in general, and I'm very happy to see them releasing athletes for next year's Olympics. I'd certainly watch another Four Nations tournament. But I can't help thinking they could just work on expanding their reach in markets that already understand hockey. Just watch a few Raptors games and observe the ad content and general presentation of that sport and you'll see what I mean: hockey seems pitched at old white people by comparison. I happen to be one of those, and I can still see it. We have diverse populations in all the big market cities, but hockey isn't reaching them.