Every successful discrimination plaintiff can point to at least one other person who received similar unfair treatment. Unfortunately, convincing comparisons often require a fairly sophisticated statistical analysis that many lawyers either don't want to do or don't want to spend the money to do right. Some types of harm are so minimal that a complaint would get thrown out of court. Being called a racial name once is not enough, for example. Multiple name-callings may get you to court, but if you only suffered embarrassment and anger and there's no money loss or lasting psychological distress, the amount of your damages may not be worth the hassle of pursuing it.
Sexual harassment is a type of discrimination that is frequently in the news.
The federal government and some state and local governments fund agencies to investigate discrimination cases. Going through these agencies is often a required first step before you can take your case to court. The majority of discrimination charges filed with the EEOC are hurriedly reviewed by overworked investigative staffs and then dismissed with a finding that the agency didn't have enough evidence to pursue the charge further. With the finding comes a notice that you now have the right to sue in court. That right expires within 90 days and if you don't sue during that time, you lose the right forever.