Beyond just ensuring that your resume looks like all the other resumes out there, templates are also generated as "one_size_fits_all" solutions. Do your career, your unique work experience, and your individual goals really fit in a one_size_fits_all format? For the vast majority of people, the answer will be no. Very few professionals have a completely linear, untarnished employment history. If there are any 'problems' in your background__such as a period of unemployment, too frequent job changes, a demotion, or any number of other challenges__a resume template will only accentuate and call attention to the negatives.
Creating your resume is important. Potential employers will be scrutinizing the resume and can tell the kind of person you are by what you include and how organized it appears. The same goes for the cover letter you send out together with the resume. It can be quite tedious trying to make the resume from scratch. Chances are you might end up excluding some important areas and including others that are not that necessary.