Many starting out on Twitter incorrectly assume that because Twitter is a social network that the following holds true: If you follow someone, they will follow you back. But the reality is that on Twitter, that quite often doesn’t happen.
Consider this, if you see an account that has thousands of followers but they in turn are only following a few hundred, you could comfortably assume that this account is sharing something of value with its audience. Conversely, if you see an account that has a few hundred followers but that account is following thousands of others, you may assume that this account is not being effective in engaging with or building its audience. The greater the discrepancy between the number of accounts followed and followers, the more likely this is true.
Compounding this issue, if you are following way more people than are following you back, many (or most) people on Twitter will be cautious, as they likely perceive you to be a spammer or overly promotional marketer.
Additionally, you can only follow so many people on Twitter before the idea of following starts to become meaningless. If you are following thousands of people, the likelihood that you’re going to get a meaningful experience from any single follower is pretty small.