Denial of Service attacks are pretty easy to launch, and there are usually five different motivations:

1. Experimenters just want to see if they can make it happen, see if they will make the news.
2. Vandals just like causing damage. If they weren’t doing DDoS attacks they would be throwing bricks through windows for no really good reason.
3. Hactivists want to make a political statement by bringing down the website of a company or organization they disagree with.
4. Cybercriminals launch DDoS attacks and then ask for financial payment to stop.
5. Nations attack other nations as part of cyberwarfare, such as Russia launching DDoS attacks against the Ukraine and other countries.

Those same five types of attackers and motivations apply to all cyber attacks, really. While the highest amount of damage these days is done by cybercriminals, DDoS has a high percentage of vandals and hactivists behind the attacks.