I am 2nd generation dutch american (my grandparents were born in Holland) so the thrifty ways were passed along from family. My father is an auctioneer so EVERYTHING we owned had been loved before. I always wore hand-me-downs from my other dutch cousins a state away and thankfully they were ahead of our rural area in the "fashion scene"' so the idea of wearing second hand clothes never made me flinch. It did pose problems with fit so I learned my way around a sewing machine at a very young age.
I think I started thrifting by going through my grandmother's and/or mother's closets when I was in high school in the 80s and I liked the look of the 50 & 60s vintage. (I still have and wear some awesome dresses from my mom, see above) So, when I discovered thrift stores in college it was just an extension of how I had always acquired my clothes. Second-hand.
I am now the mother to a 4 year old daughter who really thinks nothing of the church shops and charity stores we frequent. I hope she can continue to not be bothered by the thought of a "new dress" not really being new.