I think that one of the main driving reasons people shy away from hard work is that the relationship between effort and work is non-linear. I'll give you an example.
Part of my workout is that I do half an hour on a rowing machine. Now rowing machines let you work as hard as you can, or go as slowly as you want. Now, if I were a lazier man, I think that in my half hour workout, I could put almost no effort in and manage to go about 5500m. I think I could do that easily and I'd not be short of breath at the end and I wouldn't even break a sweat. But what I tend to do, is go as hard as I can manage for the 30 minutes, and end up with a distance of about 7000m. (No laughing!)
What gets me here, is that although I am working approximately 100% harder, I am only seeing a 27% increase in the distance I go. This seems outrageously unfair.
Another example. If I do the bare minimum amount of work for a test (which I frequently do), as in attend most of the classes and get to the exam on time, I'll normally get about 60%. If I do a lot of work - I'll define this as 10 hours of studying - I'll manage 75%. So again, this huge increase in effort (10hrs compared to 0hrs) yields only a 25% increase in performance.
Obviously, if the extra effort meant a more significant improvement in results then I'd be more prepared to make the effort. But who said life was fair?
N.B. I was going to include a lovely sigmoid graph with this post, to illustrate my point, but making the graph turned out to be quite difficult (and it would only yield a small improvement in the quality of my blog post) so I decided to go for this picture of a fluffy bunny instead.