The number of followers you have means a lot more than you might expect. Most viewers take the number of followers on an account into consideration before they decide to click the follow button — or not.
The perception of popularity is often enough to manifest this quality in real life. You could be an expert in your field, but without enough followers to “prove” it, nobody is going to pay any attention to you.
Whether you’re a new account trying to get off the ground faster, or a mature account in need of a boost, there’s plenty of reasons why it makes sense to buy new followers.
You can also buy Instagram likes.