Primers: A necessity or marketing ploy?

By definition, primers act to prep the skin for foundation by smoothing, moisturizing, or even by claiming to keep your skin mattified throughout the day. Most pertain to a silicone base and has been around the market as a must in controlling oil and an enabler in maximizing the duration of your make-up wear time. I am however, not an avid believer just yet. I have tested out a few in my day (Clarins Instant Smooth Perfecting Touch, MAC Prep + Prime Line filler, Smashbox Photofinish Foundation Primer) and all have fallen short to their ridiculous claims.

If you adhere the principles of a primer, simply a well formulated moisturizer should suffice.