...there are many exceptions of course, but science majors tend to be liberal, engineers tend to be conservative; even though their curriculum is practically identical.

Humanities and behavioral/social sciences majors are more likely to be liberal, business students are usually conservative (but not always, I once knew a BusAd major who was a communist, he just wanted to fully understand how his enemy thought and what motivated him). Mathematicians, on the other hand, as a rule, show no preferences. (That was pointed out to me by a very conservative mathematician).

Lawyers will work for either side, but still fake the orgasms very convincingly.

Market demands and social conditions may play some role in this, but I also believe individual psychology does too. For example, engineers and scientists both may have a talent for science and math, but scientists truly love nature and figuring out how it works, while engineers are interested in practical solutions to immediate problems, they don't care how it works as long as they can use it. This is not a criticism. Doctors are engineers, not scientists, their primary job is to save lives and reduce pain, not understand anatomy and physiology.

A truly successful scientist wants to move up in his career by attacking more complex and important scientific questions, while engineers can't wait to get out of the lab and into management.