The richer you are the more distant the things can be from practicality. As extensions, each purchase distances you from the direct transactions between humans and between humans and their environment, extending what's possible way beyond your own body and mind's capacity. With global communication technology, especially the advent of TV, taste boundaries and group boundaries are much more porous. Knowledge of other cultures as display of status. The T-shirt is worn on every corner of the planet, an item of clothing that is practical, inexpensive, and allows people to display images and text as part of their person.
Modern dyes allow range of brilliant, cheap colors.
Gradually see words and images silkscreened on. People display their identity through wearing shirts from their group, their college, their employer, their sports team. Most are covered, front and back with words and images. Many are walking billboards, often for products or places the wearer has little or no connection to. The T-Shirt is part of a larger trend of culture becoming independent from geography.