Selling toys
As the Industrial Revolution took hold, European and North American parents transitioned from making most toys at home to buying most toys ready made. But as the variety of toys available exploded, manufacturers began competing with each other to attract the greatest number of customers.
Very quickly, toy makers latched onto the idea that toys could be educational. The rise of commercial toys happened at the same time as the rise in the mandatory education of children. Toys, therefore, became tools to reinforce lessons or to teach subjects not covered in school. Dolls taught parenting and domestic skills. Board games were geography lessons in disguise. Toy soldiers grew in popularity whenever the United States was at war, and animal figures introduced children to both creatures they might never see in person, and to the biblical story of Noah's Ark. Buying toys made you a better, more responsible parent... or so the sellers promised.
As stores competed for customers, the concept of branding took off in earnest. While a child in 1900 could ask their parent for a doll, a child in 1971 could specify that they wanted Malibu Barbie and her Dream House. In the 1980s, a US-wide ban on advertising directly to children on television was lifted. The toy market exploded and the era of the tie-in toy began in earnest. Although tie-ins weren't invented in the 1980s -- Star Wars action figures were the must-have toy after the release of Star Wars in 1977 -- they grew in number until, by the end of the 20th century and continuing today, the toy market is almost entirely made up of tie-in toys.