Ralph Stinebrickner and Todd Stinebrickner say lots of kids come into college thinking they want to major in science, but then quit because it's too hard:
Taking advantage of unique longitudinal data, we provide the first characterization of what college students believe at the time of entrance about their final major, relate these beliefs to actual major outcomes, and, provide an understanding of why students hold the initial beliefs about majors that they do. The data collection and analysis are based directly on a conceptual model in which a student’s final major is best viewed as the end result of a learning process. We find that students enter school quite optimistic/interested about obtaining a science degree, but that relatively few students end up graduating with a science degree. The substantial overoptimism about completing a degree in science can be attributed largely to students beginning school with misperceptions about their ability to perform well academically in science.
This is important to keep in mind when you hear people talk about the desirability of increasing the number of students with STEM degrees. To make it happen, you probably either need better-prepared 18-year-olds or else you have to make the courses easier. But it's not that kids ignorantly major in English totally unaware that a degree in chemistry would be more valuable.