There are entire books written about this topic, but one thing to note is that research suggesting that being married is better than being single does not hold up well to scientific scrutiny.
One major problem is that the research ignores people who get divorced. Researchers throws out data from more than a third of the sample (i.e., people who get divorced) and then conclude that married is better than not. Given how devastating divorce is—financially, emotionally, and psychologically—to ignore that sizable group, falsely bolsters the benefits of marriage.
Moreover, previous research fails to differentiate people who want to be partnered (and aren’t) from people who are single by choice. That is an important psychological difference.
Lastly, there are many ways to measure a good life. Single people, as I say above, have great opportunities to live unconventionally. Singles do a lot for the world; they are more involved in their community, they donate more time and money, they contribute to science, art, and literature—and so on. Listen to the podcast to hear more.