Unfortunately we have clients incorrectly use private information for member numbers. Many schools use social security numbers for example. They should NOT, but they do. We can't stop this from happening when custom forms are out there.
Thus the default templates for notifications do not include the member number. In fact email notifications submitted by non-confirmed/approved submitters should not contain any input submitted by the user. This is because they will enter information like
First Name: <script - bad stuff here>
Last Name: www . bad web site here . com
Email: SOMEONE ELSE'S EMAIL HERE BECAUSE THEY'RE SPAMMERS!
That would auto-reply to whoever got on the spammers email list from your web site using your email address and they could write a script to loop through it. One more reason we enable Captcha by default and that email auto-responses for anonymous submitted forms shouldn't auto-reply.