Great points at the end K. I think this has to do with commitments, time and money. The older you get, the more commitments there are to work and an ever increasing family (in the majority of cases). I don't think your tatses are fixed in one era, its more a case of people having children and spending less time with new music, clubs, record hunting or whatever. Your career also takes off mid-twenties/thirties leaving less time for the frivilous enjoyment of music. Before you know it, there's a plethora of music you've missed, decades of new bands/new artists and you no longer have the will power or interest to listen to new music. The older you get, the more entrenched you become in the familiar. Not everyone...but certainly the majority.