Why do people buy domains?
There are many reasons why people buy domain names. It is however for the most part split into two sections, and both of them can make you money (if that is what you’re looking for). The first is for personal or company use on a website, while the second is for domain resell or parking.
Website
Now there are plenty of ways to make money off of a website. You can create a one of a kind site that draws people and therefore by putting ads on it you can make large profits. The other option is to develop a site (ads or not) that becomes extremely popular and then sell it as a package of the content, the domain, and the network of users.
You can also just use it as a personal way to express yourself or your interests if it isn’t profit that your looking for, but just a way to spend your extra time.