People who don't need to print anything bigger than 4R would buy a camera than can print only a 4R picture.
Are you telling people not to join photo competitions because it's too expensive, chances of winning too small etc? The choice is up to the photographer lah, do what he/she enjoys ....
Anyway, there is a very cheap alternative.... go shoot some digital photos of the contest theme (don't print, save $$$!), then compare them with the winning entries, if you think you made a better shot, then you got some personal satisfaction. After all, one of the earlier posts did remark that "crap work" had won photo contests before. And beauty is in the eye of the beholder.