Looking at my chemistry class (12 students at an Australian secondary school) quiet a few are failing the subject. Why? They find it rather boring, the concepts are not something interesting to them and somthing that might explain some questions that are out there in our world, it's something they have to learn (and understand which is more often the problem). Although our teacher tries to make it as practical as possible by giving us quiet a few lab sessions each semester, most people dread this class when it comes to exams. To really understand chemistry, you have to wrap your head around quiet a few concepts and know how to apply them.
I guess that scares off a lot of people (even the better students) to apply for straight chemistry. They rather do another science - biology or physics - in which they have to do a bit of chemistry, too. But it will not really go into depth as far as the concepts go.
Personally, I am applying for chemistry because out of all the sciences, it is the one which fascinates me most. It provides explanations to me. The idea that the entire universe is made out of the elements of the periodic system is quiet fascinating to me. Well, that is my opinion today - I'll see how I feel about chemistry in a couple of years. Maybe I am quiet sick of it and want to get out of it, but hopefully I will still enjoy it as I do today.
As to my above mentoined chemistry class, I am the only one applying for chemistry. One girl is applying for medicine, but everyone else does not apply for anything remotely to do with this science.