“As long as an individual consumes a varied diet that supplies adequate energy, vitamin and mineral needs will likely be met as well” (McGuire & Beerman, 2018). The Mayo Clinic also says that certain supplements are more important depending on one’s age or life stage they are in (Mayo Clinic, 2017). Therefore, it may be beneficial for athletes to supplement with iron, calcium and vitamin D for those over 65, zinc for those that limit meat intake, and folic acid or folate for women who may become pregnant (McGuire & Beerman, 2018). However, when it comes to a daily multivitamin, most research agrees that this is not necessary as long as nutritional needs are being met through a variety of food sources. So the question becomes: "Are you getting your nutritional needs med through a variety of food sources?" 

I would argue that nutritional needs are not being met for a large part of the population. While research says that as long as one is getting a variety of healthy foods in their diet they do not necessarily need to supplement, I would argue that this is not the case for a significant amount of the population. Furthermore, the Mayo Clinic lists several reasons why it may be necessary for someone to supplement with the first reason being if an individual does not eat well (Mayo Clinic, 2017). According to a study done by the CDC in 2015, ~12% meet the recommended intake amount of fruit and ~9% meet the recommended intake amount of vegetables (Lee-Kwan et al., 2017). Certainly one daily multivitamin will not fix an otherwise unhealthy diet, but based on the question and what the current eating trends in America are, I would say that most people should be taking a daily multivitamin. Perhaps the small percentage of people that are consuming a variety of healthy foods do not necessarily need a daily multivitamin (although they may benefit from other supplements depending on age, etc.). However, a diet mainly consisting of highly processed foods and few fruits and vegetables is likely causing many nutritional gaps.   

Below is an interesting figure from health.gov. This shows the percentage of people in the U.S. that are currently getting below the recommendations of healthy foods as well as the percentage currently getting more than enough of the recommended amounts of added sugars, saturated fats, and sodium. Therefore, those that fall in the category of not meeting the recommendations may benefit from a daily multivitamin.  

Dietary Intakes Compared to Recommendations. Percent of the U.S. Population Ages 1 Year and Older Who Are Below, At, or Above Each Dietary Goal or Limit

Retrieved from: https://health.gov/our-work/food-nutrition/2015-2020-dietary-guidelines/guidelines/chapter-2/current-eating-patterns-in-the-united-states/ 

So now the question is: "Which category do you fall in?" Especially when it comes to fruits and vegetables which contain many essential vitamins and minerals, you want to ensure that you eat the recommended dietary amounts. If you don't, you may want to consider a quality daily multivitamin.   

References

Lee-Kwan SH, Moore LV, Blanck HM, Harris DM, Galuska D. (2015). Disparities in State-Specific Adult Fruit and Vegetable Consumption — United States. MMWR Morb Mortal Wkly Rep 2017;66:1241–1247. DOI: http://dx.doi.org/10.15585/mmwr.mm6645a1

Mayo Clinic. (2017). Supplements: Nutrition in a pill? Retrieved from: https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/supplements/art-20044894 

McGuire, M., & Beerman, K., (2018). Nutritional Sciences: From Fundamentals to Food (3rd ed.). Boston, MA: Cengage Learning.