WordPress has just about any plugins you need, from social media, to even building your own simplest contact form with just a few clicks. This massive library of plugins makes you think about not doing it yourself at all.
So, why bother building your own Contact Form when you can do that with a plugin?
This is because plugins for a simple contact form has more than everything you need. Building a simple contact form using a UI is overkills, and the good thing about building your own is that you know what is under the hood; therefore, you won’t worry about being hacked, getting your visitor’s emails compromised, etc.
Here are some reasons why you need to build your own contact form than rely on plugins to do it for you: http://wpmu.org/how-to-build-your-own-wordpress-contact-form-and-why/