No, you don't need it but yes, it is helpful! You have to complete so many credits in college anyway (just like classes in high school) and depending on your major you'll have extra time in your schedule for electives. You could take a variety of different things you're interested in or you can put that focus into another major or a minor. This shows a deeper knowledge in one area rather than a superficial knowledge in many areas. Some majors/minors go well together and others seem haphazardly paired but either way I think it is beneficial to focus your studies and get something else out of it. You never know, in the future you may find your second major to be the focus of your career. Or if you end up working in your primary field, you can use that secondary education to diversify your brand and make you stand out to certain companies over your competitors.