Also, some of us might simply be busy. I've got at least two other games/communities that I participate in, one of which is a place where dozens of roleplays take place. In magicduel alone I'm trying to be a Protector, run the Coloured Paper, and help to mod the forums. Although I probably could easily find the time to work on my plot once in awhile, it feels too much like work if I try and do it regularly.
Mind you, some of that is probably because I need to make a schedule. I bet that I'd be able to work on my garden once every week or two weeks. The problem is, giving rewards out for something makes it seem like work, at least for me. I know at least one person here who has held this view way before me. If I wasn't expecting rewards, I'd just be working on my plot for fun. But since I'm trying to plant things with the goal of a real harvest, the planting and growing feels like work.
Although Magicduel might be 'more than just a game' to some people (like myself), I still play it for enjoyment and the (ideally) regular mental stimulation. Often though, I do things in magicduel not because I particularly enjoy doing them, but because I think they have potential. The problem is, the Community Garden has become yet another one of those things.
I'll try and work on my plot more. People (like myself) often lack dedication in general. Those who don't lack dedication, dedicate themselves to what they feel is the best use of their time. But, sadly, I am in University, taking classes in the spring-summer term. Therefore, I am somewhat busy with school, other magicduel things, and other games. I also know that most people are probably way busier than I am at the moment, and I count myself lucky. (I'm an English student).