Jerry, we had this discussion before, I'm pretty sure.
The bigger the file, the longer it takes to send/receive and the more space it takes to store. Bandwidth costs money, and once a website surpasses certain bandwidth limits, the costs rise, quite sharply I believe. This is a free site, so the owners have to set some limits. When someone else views images that have been uploaded, those images also count toward bandwidth limits.
Sites like photobucket are great. Free storage, and the links that you post to images use photobucket's bandwidth, not this site's bandwidth.