Yes, celebrities have a lot of followers. But isn't that true outside of Twitter as well? As of publication, Ashton Kutcher has 2,286,717 followers on Twitter. That's more than CNN Breaking News (1,866,804 followers) and Twitter (1,485,347 followers).
When you sign up for Twitter, anyone can read your tweets and choose to follow you (or not). If it's a lot of followers you're looking for, you'll need to work for it. Fill out the bio, share photos, use hashtags and keep on tweeting. Tweet about what you love, not what you think your followers want to hear. They're following you because they find you interesting, not a fake you. Retweeting (RT) will also help spread your name around.
Some Twitter users don't use the tool this way and choose to keep their tweets private. With a private account, you select who may or may not read your tweets; it's sort of a velvet rope you use to create your own private twitter feed. Who says a lot of followers is a good thing, anyway? Shouldn't it be quality over quantity?