The belief a ‘generational cohort’ eg “millennials” are somehow qualitatively different from previous generations at a similar stage in their lives.
If you believe this, I reckon you are more likely to look for psychological explanations of their behaviour - i.e. more of them are staying at home because they are lazy or dependent, more of them are taking short-term jobs because they are uniquely adaptive, etc.
On the other hand, if you believe that young people are NOT inherently different from any previous group of young people - i.e. that apparent attitudinal differences are basically a function of age, not ‘generation’, then you’re left looking for material reasons for behaviour change, and have to start thinking uncomfortable thoughts about eg. the economy, job prospects, the choices made by people now in their 40s and above, the structural differences and power relations WITHIN a generational cohort.
I reckon this is one hidden effect of the widespread acceptance of generational segments and stereotypes, eg the easy belief that the word “millennials” is useful - it pushes people towards psychological, not material thinking.
Inspired by this gross advertising campaign: http://bbwgetsyouahead.com/