Here is what I observe:
When I select a contact and click the option to create a message, almost all my contacts have many possible addresses this message may be addressed to. Examples:
- Email address (which may be an Apple ID)
- iPhone telephone number
- Mobile telephone number
- Other telephone number (as it cannot yet be determined which are valid telephone numbers to receive messages)
So naturally in the above case, you must select the correct address to send the message before proceeding.
Those very few contacts that have exactly one candidate place to receive a message do indeed send me directly into the text box. But these contacts are the exception.