Templates can give your work a professional look almost instantly, and are particularly helpful when you are getting to know a program or don't have much time to finish a project. At the same time, there are certain disadvantages to using templates which apply across most of the applications that offer them.
As pf September 2013, more than a million users have subscribed to the Microsoft Office 365 Home Premium package, so if you're going to be using one of the suite's templates, then the chances are that you're not alone. If you're putting together a document that needs to be unique, such as a resume, then you don't want to have to settle for one of the pre-existing templates. Using templates can make it more difficult to stand out from the crowd and can give the impression of unoriginality if your audience has seen the same format many times before.
The quality of available templates varies from application to application, but in many cases you might find the choices are rather basic. Some templates rely on you to fill in most of the gaps, and may have graphics or visual elements that are below par. You might find that using a template produces an end result that's less impressive than something you could have put together completely by yourself, and if you're looking to show off your work or your skills -- on a photography portfolio website, for example -- then this can count against you.
Relying on templates to put together your projects, whether presentations for the office or personal websites, means you don't get the benefits of learning the ins and outs of the software you're using. Putting together documents of your own from scratch forces you to educate yourself about the features of the software in question and the ideas behind them. Should you be using the relevant programs for work, taking a template-based approach can stop you from learning about and exploring the software as much as you otherwise would.
Application templates are usually designed to help you produce results as quickly and as conveniently as possible, but in many cases the customization options can be limited, restricting what you can do with your files. If you aren't familiar with the product in question, then it's likely that you won't know how to make the necessary edits and modifications to the template to make it your own. In other cases, the template won't be able to be customized in the way you would like, leaving you with an end result that you're not happy with.