Templates are a good starting point for presentations. They guide you in the sense that they provide consistent font styles and sizes that user are able to read.
While being helpful at first, they are also a bad thing:
Some companies tend to place their logo and sometimes even more on every slide. That reduces the space for your own content.
In my opinion, it is much better to use images to spread the message and give a handout to your audience if you want to provide more detailed information.This helps them to understand your objective without having to present every minor detail.