Perhaps they've been sheltered for too long by their "helicopter parents" or have become complacent about their worth after a decade of boom, or perhaps they are just plain different.
Whatever the reason, more evidence has emerged to suggest that Generation Y workers are posing, and will continue to pose, huge headaches for employers.
Generation Y employees or those born since 1980 are generally flighty, badly organised, poor at planning their workload and less efficient than other generations, according to research among 4,000 people by UK people assessment firm Talent Q.
But it's not all negative. They also have great social skills, consider themselves to have high ethical standards and, slightly contradictorily given the finding that they are badly organised, are good when it comes to attention to detail.
The latest findings add to the growing body of evidence that Generation Y are posing unique challenges for employers in an ageing workplace where youth is becoming an increasingly precious and sought-after commodity.
A survey a fortnight ago, for example, by Princeton-based consultants BlessingWhite suggested that in almost all parts of the world except India employees born since 1980 are the least engaged members of the workplace.
Its poll of more than 7,500 individuals and 40 senior human resource and line managers found that the more senior the employees, the more engaged they were.
The Talent Q study is intriguing because one of the most common assumptions about Generation Y up to now has been that adapting to rapid change is what they are really good at.
Not necessarily, argued Talent Q chairman Roger Holdsworth. "The days where a person has a job for life are long gone, so it's perverse that the 'Generation Y' psyche appears to show less adaptability, efficiency and dynamism than older generations," he said.
"The 20-somethings we studied were also less resilient, less confident at negotiation and decision-making, less influential in a leadership capacity and less able or willing to follow the rules all of which is concerning for the future," he added.
"But there were positives too. In stark contrast to popular perceptions of surly, selfish and aggressive youth, the younger generation claims to have a stronger ethical code, is more socially aware and more in tune with other's behaviour than their elders," he continued.
The research also examined some of the stereotypes around older generations, particularly the assumption that they are more conservative and "set in their ways".
In fact, it found the Baby Boomer generation was the most likely to adopt new techniques and most likely to favour radical ideas.
However, the same generation were also found to be less socially confident, less ambitious and less likely to fit in with different types of people.
"Perhaps because of growing up in the 1960s, radicalism still shapes the Baby Boomer psyche," argued Holdsworth.
"They remain more adaptable to change than younger people very much confounding the view that 'you can't teach an old dog new tricks'," he said.
"But Baby Boomers also, perhaps understandably, show signs of easing down as they approach retirement, showing less ambition and competitiveness than other generations," he added.
"The research also suggests the stereotype of grumpy old men and women has a grain of truth to it. Our studies found that the Baby Boomers were generally less socially adept and comfortable with different people than younger generations," Holdsworth concluded.