Since the 1950’s and even earlier, screen printed t-shirts were everywhere. It was the only way to provide a custom decoration. Other decoration was done using iron-on designs or transfers, resulting in a “decal” looking product with very limited. wearability.
Many people remember the transfers from the late 1970s and early 80s as thick rubbery designs with one color. They would sometimes crack or peel. This process is very labor intensive and takes a significant amount of time to perform.
Screen printed t shirts was much more efficient. Allowing printers to do multiple t-shirts faster. Although relying on toxic inks, screen print shirts are still a standard in the t-shirt printing industry.