I get hung up on the application of the term culture here. I'm not sure there is a connected mass large enough worldwide to be considered a definable culture with regard to custom made steel bicycles.
When I think of the cultural relationships that bicycles have to groups, I think of the Dutch oma/opafiets bicycle within that culture. I think of the English three speed. I think of the Italian "sport/city" bike. French rando, maybe. They could be custom bikes, but certainly didn't need to be, and most of the time were not. Were those cultures not better served by the availability of product, than by the small-time local guy who couldn't possibly provide for demand? Bicycle racing is important within some cultures, but technology has moved on there.