Pretty sure this is it. I hail from a third world country, but I have never faced any issues since I'm European, and have since "whitewashed" my passport into a Five Eyes one.
Have even cracked a joke or two with TSA agents & gotten a "Welcome to America, enjoy your holiday" at LAX.
My point is that I'm the exact demographic of people who should be getting hit by "random" searches and I've got the volume of travel where it should be happening to me somewhat frequently if it is a widespread issue that occurs with any regularity. I'm 24-34, 1/2 Arab, have a beard, book a lot of flights on short notice, sometimes just one way, and NEVER check a bag.
I don't get ever get bumped from flights and I get pulled out for "random" searches on average of 1 times per year for the past 5 years.
Again, all anecdotal, but I'm the definition of the guy who should hate the airport. I only just dislike it.
Have even cracked a joke or two with TSA agents & gotten a "Welcome to America, enjoy your holiday" at LAX.