I'm using BuddyPress to allow users to log in on the Front end. Once logged in, they can click on 'My Account'. On this page they can upload avatars, edit their account information, etc.

When I upload a new avatar from this page, the 'profile_update' hook does not fire.

If I remain logged in as the same user and navigate to the backend (/wp-admin) and upload a new avatar from there, the 'profile_update' hook fires successfully.

Why would the hook only fire when accessed from /wp-admin and not the website front end ?