Many people will use a webmail service such as Gmail, Outlook, or Yahoo without having an email app setup or even installed. By offering a contact form on every site, it will allow visitors to simply use the contact form to send a message. The message will then be sent to my email address where I will be able to see which site the message was sent.
Such messages are replied to, and then deleted. If you would want to have a standard correspondence, you would be best to use my email address which I keep messages from that source.