I'm not sure why this is so hard to comprehend. Just like almost anything else in life, there's a bell curve.
In this case, that means a few people travel almost every weekend, a few people almost never go anywhere, and ~90% of the class will leave the Boston area 1-2 times per month.
Some of those trips will be vacations, some will be section events, some will be related to job-hunting, and some will be through clubs. This "lucrative" ski trip they keep referencing was billed as the official class ski trip, but all that meant was that the student leadership was able to negotiate discounted rates through the hotels and ski resorts. It fell on a long weekend, so a decent chunk of the class went. But there's no expectation or requirement that you go anywhere at any time. Some people have the money to travel a lot--not to mention the intelligence levels necessary to do well academically without working too hard--and some don't. That's pretty much all there is to it.
None of this stuff is unique to HBS--for instance, I knew people at Haas and Stanford who basically lived at Lake Tahoe during ski season. Students at other east coast schools go to Europe occasionally on long weekends or for events like Oktoberfest.
And again, a huge majority of the HBS class does
not go on extravagant vacations on a regular basis, but their lives don't make for interesting NYT hit pieces about the opulent, over the top lifestyles of HBS students.