But a recent report suggests they should be trying to accommodate Baby Boomers instead.
"While addressing older shoppers is often perceived as less sexy, they are a larger segment of the population than those under 35 and have significant disposable income," writes Sucharita Mulpuru at Forrester Research. "They are already spending more on shopping than young shoppers."
Millennials, defined as people aged 20 to 35, are spending less on consumer goods because of expensive healthcare and education costs.
But Baby Boomers, who are aged 51 to 69, are the "biggest spenders" because they have extra cash from decades of saving and investing, according to Forrester.
Older shoppers also make up a larger segment of the population than ever before and could meaningfully influence
In 1973, older consumers comprised 25% of discretionary spend; by 2013, they drove 35% of all discretionary spend, according to Forrester.
They're also the only consumer segment that has made gains in real income since the 1970s.
Forrester Research
Still, retailers tend to market to young people in hopes of making them customers for decades to come.
Mulpuru believes this strategy is flawed.
"Consumers are often willing to try new things, and the availability of greater choice and cheaper goods means that few retailers are able to hold on to customers for very long without significant investments in their products or promotions," she writes.