Or they want to deposit or re-invest bitcoin so they also have to buy bitcoin. But I think people are looking for money through bitcoin like I will not buy bitcoin
Most people buy bitcoin so that they can make quick profits out of it. The way you wrote this seem like you're in it for the long term and you don't really need bitcoin in your everyday life to buy stuff. Since you're not spending any money on bitcoin, making profits for you will probably take longer, there is nothing wrong with this method, it's just other people like to do things differently. It's all just personal preference.