Too Old Too Soon

I am 26. I am restless, idealistic, romantic and fearless - the sub-definitions behind the word "young." So when did being in your late-20's signified "adulthood" - obtaining another degree to enhance career opportunities, settling down with one person, buying real-estate, investing in retirement plans and essentially giving up aspects that signify youth. What is the hurry to plant a permanent stake in a 7,000+ sq. ft. lot for 20+ years? Ironic that even though our generation - in comparison to our parent's and/or grandparents' generations - has an array of opportunities line up for us to choose, we still turn back to the traditional choices that limited previous generations. When did the concept of getting married and having a family have a timeline? Do we doubt ourselves so much as to say, "I need to lock down this person for they are the best I have found" in our mid-to-late 20's? Is it a blame on this increasingly conservative Western culture? Or is it a blame on our own personal insecurities? One can only wonder.