Well, imgur was originally created by a Redditor specifically to have an image hosting site that wouldn’t take down images for any reason or disable hotlinking like all the other ones eventually do.
It became the de facto image host for Reddit, then kind of grew into its own thing with its own community.
Somewhat recently, Reddit has provided the option to host images on Reddit itself, but imgur is still very widely used by Redditors.
And that concludes your internet history lesson for today.