Aside from stealing patents and intellectual property, they want to gather a lot of information on anything. As Mr. Juneau-Katsuya said earlier, they get anything they can and then they sort through it.
When it comes to the collection of personal information, I can cite the Office of Personnel Management, in the United States, which had anything that constituted Americans' personal information stolen, including security clearances.
The data stolen from Marriott and Equifax means that there is an information pool that makes it possible to take interesting photos, as facial recognition also comes into play. Around the world, a network is being established to catalogue people.