When one turns 30 a commitment (often subconsciously) is made to a higher standard of overnight accomidations when away from home. Though some gifted individuals may make this transition at an earlier age, there is no more powerful catalyst than the chronological clock striking 30.
There are a multitude of factors that contribute to the decision that sleeping in youth hostels, in cars, or on floors are no longer acceptable forms of lodging for a 30 year-old.* Every Triple Decker knows well that to properly recover from even a single night on an unforgiving floor or couch, hours must be added to the next morning's stretching routine. And heaven forbid a Triple Decker set foot in a youth hostel! They know they will be the instant object of scrutiny and will most likely be referred to as "that weird 30 year-old in the 16-bunk room" or be accused of being a degenerate serial killer who preys on young hostel dwellers.
Many Triple Deckers make it a point of personal pride to treat themselves well as they travel. This is especially true for those who are financially fit, or who at least have some sort of business expense account they can make use of (whether justified or not). If a Triple Decker is a proud home owner, there is a near-zero chance that they will settle for anything less than full comfort while away from home; "I'm a home-owner! I deserve a bed of my own!," is the mantra of such Triple Deckers.
This sea change in sleeping arrangements explains why so many at or near 30 are well-versed in travel websites, collect travel coupons, and have multiple rewards club memberships; so they may experience the greatest amount of comfort while traveling. They also are careful to stock their own dwellings with air mattresses, sleeper sofas, guest rooms, or some combination thereof so that they may pay it forward when other 30 year-olds come to visit them.
* Exceptions to this rule are granted for extreme financial hardship or inebriation.