Why do webmasters do link trading?

Why do webmasters do link trading? For some reasons, it’s because they want their site to be more popular than the other. They want to improve their sites as well, in a sense that, it will take the internet search position. When you said internet search position, it means that their site will show up into the top and not on the bottom search results. And this is a great advantage for those sites on top because mostly, people will notice the link or automatically click the link when it’s on top. And by clicking it, the site or the search engines will rank them higher if they have the said high link popularity. The site will also be revisited more often.