Some dishonest people share nulled files for hacking purposes. But not everyone. Some people like me share these premium files for free. Therefore people like you could try those premium plugins before purchasing them. In fact, I bought all the plugins. As I'm a PHP programmer, I understand how to read and write programs of a theme or plugin. Actually programmers try to learn something new, especially programming related problems solving. That's why I like to learn the way that the plugins author follows to create a plugin or theme. Whenever I find out their encryption methods to limit access to their plugin, I just modify their code for unlimited access. Moreover, I can earn money through Google Adsense through my blog. In fact, I like to have good comments on my blog from visitors.