While that's true for some people, many use internships and summer jobs to find out whether a particular career path fits them. As Dr. Jones pointed out in a post yesterday,
"A lot really depends your openness to experience, being an active learner and explorer -- and using your values and interests as your career compass."
Pursuing an internship in an area you find interesting, but don't necessarily believe is the only career path for you, is a smart career exploration exercise. I interned with law firm one summer, and in between my junior and senior years, with an affordable housing and community gardening program through Project '55, a wonderful public service internship organization. I learned a lot about myself, working with other people, and community.
I know it takes a lot of time and effort to write a resume, cover letter, and to "pitch" yourself for an internship, especially when you're not sure it will be a success. On the other hand, it is better to find out what you're not suited for, so you spend time later on other more compatible fields. I remember from college several people who did internships with investment banks and hated it (but liked the money and being in NYC) - while others loved it. All these people learned something useful and for those who hated it and went on to do other things, it didn't ruin their ultimate career path.
My suspicion is that some students don't want to do the work to get the internship - more laziness than purposeful decision. Procrastination is an art form in college - I admit I occasionally suffered from it!
What kind of internship experience(s) have you had?