Indeed, rice is filling and cost-effective. Home cooks know this, and so do professional chefs - which is why, when folks order a burrito at a Mexican restaurant, there's a good chance it's stuffed mostly with rice. Many restaurants do this because rice is simply cheaper than other, even more desirable ingredients. In fact, the fast-casual burrito chain Chipotle has caught major backlash for this very practice.
Mexican food has become one of the most popular cuisines in America, and in the chain restaurant sphere, there are two spots that absolutely dominate. While burgers still dominate the lists of largest chain restaurants in the U.S., for years, the "international" food that the country couldn't get enough of was Italian. Propped up by pizza's enduring popularity, it was the food Americans ordered most, and it still is, but Mexican restaurants have been rising rapidly, and Mexican has already overtaken Italian with younger generations.
Chipotle's food safety crisis in 2015 demonstrated that the commitment to quality can create vulnerabilities in maintaining high-integrity supply chains at scale.