If it was about that, then they'd open those lines to anyone who had been vetted by the government already. They don't. The lines are open for those who pay.
Please feel free to correct me if I'm wrong (I use the TSA PreCheck program, which I paid for, but am not a US government employee with a security clearance). But I believe that if you've already been vetted by the US government in terms of a security clearance or a DoD ID then you don't need to pay for PreCheck, you can just use those lanes automatically. And the average US civilian/military security clearance investigation costs upwards of $50K.
Not to sound like a PreCheck fanboy, but if you fly more than a few times a year it is absolutely in your best interest to pay for PreCheck. Basically they look (from what I understand) to see if you're a felon, are on a no-fly watchlist, and/or have firearms related offenses or "I freaked out in the airport when they frisked me" issues. They take your fingerprints, too.
If you don't have any concerns with the above, then the $85 that PreCheck costs (for a five year term) is amortized over the cost of your time waiting in lines over five years in airport lines. I can't speak for every airport, but in Seattle the time differential between PreCheck and general boarding is often 45 minutes of waiting or more, as well as not having to take off my shoes, not having to take my laptop out of my bag, and generally being treated more like a human being than a Gitmo detainee.
You can make a cogent argument that none of the above is necessary and that it's all Security Theater. But you can't say that PreCheck is something for the one percenters when it averages out to $17/year. If you fly more than a couple times a year - and you value your time - then it's a no-brainer.
Do I believe that the government should prefer a "safe by default" rather than a "safe by exception" profile for its citizens? Yes, absolutely. There's no reason that an 85-year-old grandmother from Minnesota in a wheelchair should face a pat-down and the same security precautions as a 23-year-old Syrian national. I've flown to Israel multiple times (on El Al) and their security precautions (while undoubtedly invasive to anyone) are tailored to the perceived "risk profiles" of the passengers.The US should absolutely tailor its security procedures to risk profiles.
But the TL;DR version is that US security screening, for all its faults, isn't based on who can pay. It's based on an assumption (however faulty) that everyone is a potential terrorist, and that those who fly a lot can make an effort to show that they are less of a risk - at a very low cost when averaged over how often they fly.