Single people do realize that they experience more discrimination than couples do, on average. According to Psychology Today the more people saw single people as part of a group, the less acceptable they thought it was to be prejudice against them. If single people came together in solidarity, it would be less acceptable to judge them. Single people are targets of discrimination in many aspects of life.
Single people who identify as a sexual minority such as gay, lesbian, bisexual or asexual experience even more discrimination. When coupled people were asked if they think it is okay to judge singles, it was discovered that being prejudiced against single people was considered more acceptable than being prejudice against any other group.
In studies of happiness we found out that single people typically rate themselves on the happy end of the scale. It was also discovered that married people do not become lastingly happier than they were when they were single. Single people were expected to be unhealthier as well but it was discovered that 92.6% said their health was good or excellent. So maybe it's best not to judge!