Money can pay for new features like the ability to upload videos or keep images longer etc. Currently I think images older than x years get deleted, money can solve this.
Thought experiment: Reddit has 400 million weekly active users. Let's say PieFed grows to 10% of that.
That means that there will likely be multiple instances with over 4 million weekly active users, how do they pay for that? Who pays for all the images (and hopefully video) that those users share?