Email by private email address? Why ? and how and who?

Just had this email and never had a email to my private email address before?
does anyone know what it is about? or who this Martin Pratley is? and why not use our bader address?

Thank you for your service with the RAF Air Cadets. You have been invited to participate in the “RAFAC CFAV Exit Survey Aug 19”
To participate, please click on the link below.
Martin Pratley ([email removed])

See here: