Why does Siri offer to use email address when asked to text someone?

Why does Siri now offer to use email addresses to send text messages?

For example, I only have one person in my contacts called ''Adam''.

If I ask Siri to ''TEXT Adam'' the reply is ''what of these should i use?'' and it brings up a choice of his mobile number and his email address.

If I ask Siri to ''EMAIL Adam'' (the same person) it does NOT ask me to choose his number or his email. It just gets on with composing the email subject and body as expected. So why cant it do the same with text messages and just use his phone number?

Really annoying.