I burned my bra (well, stopped wearing one) in 1971, and other than loads of eye make up in the late 60's never wore foundation, much less primer. Fast forward many years, and one of my daughters is getting married. One of those big weddings, and I'm MOB. I felt some pressure, and resorted to a proper bra, and bought primer, foundation, eye stuff and lipstick for the day. I can tell you - what a difference it made. Even skin tone, and the primer worked wonders, as the foundation that evened out my skin tone (much damaged by spending as much time as possible outside) remained good, from 8am when it went on, to midnight.
It's still sitting in a drawer if anyone wants a go!