There is a LOT going on in the Discover tab of your Twitter account.
After all, the more people you find engaging on Twitter, the more time you spend on site; and the more time you spend on site, the more money they'll make when they find an effective way to monetize.
You can give Twitter access to your email accounts so it can search all of your contacts and find and follow the ones who are already on Twitter and probably send pesky messages to the ones who aren't that maybe they should be.
You can get a bird's eye view of what's going on with the people you are following, what they're talking about, who they're interacting with and how. And, you can find and follow accounts in categories that interest you; just search on the topics you really dig and surf who comes up.