Work experience, paid or unpaid, is an asset. It shows that you're able to function in the "real world." When reviewing an academic record, admissions committees take into account the hours per week an applicant has worked during the school year. Experience that is relevant to the profession you hope to enter is especially an asset, and is a requirement for those seeking admission to veterinary programs, dental schools, and osteopathic medical schools. The point of gaining relevant work experience (whether it is paid or volunteer) is to spend time in an appropriate environment so that you can make a better-informed career decision, and so that the admissions committees have confidence you know what is ahead of you.