The leaderboards have always been something a look forward to in games. Sadly, minecraft's farming leaderboards are more about time spent afking rather then skill.
Here's some examples:
Sugarcane - simply put a rubberband on both triggers - bam! you're farming over 3000 an hour
Mushroom - same idea! rubberbands are handy, aren't they?
Milk - Put a rubber...wait, didn't I already use this?
Pumpkin - Do I even need to say anything? Rubberbands = makes me a pro minecrafter!
Wheat - Finally! a real farming challenge!!!
So in theory, wouldn't it be much more of a challenge if something like melons were implemented? Atleast for those you'd need a silk touch for the blocks and if it were to be melon slices that would solve it better.
Problems are that the leaderboards reset in spastic intervals and are stupidly easy to cheat, and you can throw on top how it randomly gives people 55,000+ of one stay for no reason. I finally gave up caring after losing over 100 spider jockeys. Until they delete it so cheaters can stop advertising and add personal statistics, I don't see there being a need to add any more.