Most of them just want attention. Someone sees their name on the ballot and starts asking around, or it gets into the news that some celebrity is running. I've seen a few people on the internet ask about who Richard Duncan was when they saw him on the ballot in 2016. And so many articles have been written about Kanye's run.

Though some of them want to bring attention to certain issues, but they're a minority. I generally think that third parties are better for that, but if you don't agree with any of them, running as an Independent is your only option. Even if you do agree with them, there might be an issue you really care about that they disagree with you on. Jade Simmons, for instance, is one of the more centrist candidates, but doesn't agree with centrist parties like the Reform Party, while a Libertarian like Joe McHugh disagrees with the LP over environmental issues.

Personally I just wouldn't run, but they do have their reasons. I believe it's best to start off at the local level and get serious name recognition before trying higher offices. I made this video just as a fun research project, and I do specifically state that they won't win, so it's not like I'm promoting the idea that they have a chance. Again, just run for some local offices, people.