If you watch the FCC enforcement actions, you occasionally see them going after a truck stop, or a good ol' boy CB shop that's probably located behind a truck stop, for selling export radios or CB amplifiers. It's rare, but it does happen.
Oh yeah, I've seen the occassional CB enforcement, but those are for American distributers. The problem with CCRs is that not only are they made in China, but they are generally distributed from China. There is no enforcement to be done. Sure, there are some middlemen and dealers in the US, but you simply cut them right out of the loop. The end user is always going to be able to go on Amazon or eBay or Alibaba and have the radios shipped to the US. The government can ban their import entirely (which isn't going to happen) but then Customs will simply miss it like they do every other "illegal" item that is imported into this country. It's not their priority to catch illegal radios.
Sadly, I have to agree with Chronic on this one, that this is the Big 3 getting angry about losing sales. This is not about interference or radios not meeting the FCC specs. or what have you.
Sure, no public safety/service agency is ever going to be using CCRs, and while that segment is a large chunk of the people who purchase radios, my guess is that it hardly compares to the number of radios that are purchased for business use. You can have factories with a couple thousand radios, you have school districts, local governments, water companies, electric companies, consumers buying $50 a piece bubble pack radios, etc. Where I used to live, the school district, for example, had far more radios than the Sheriff/Fire Department/EMTs combined. Wasn't even close.
Make no mistake, the CCRs are absolutely 100% cutting into their sales, whether anybody cares to admit it or not. I see it just casually going around my town here. Small businesses have the Baofengs, some smaller local utility companies have the Baofengs, a local private school has a combination of Baofeng and Retevis. Outside of one guy using a Midland mobile radio, I haven't come across a single GMRS user out here who isn't using a CCR, and it's largely the same on MURS.
Las Vegas? Los Angeles? You don't even want to know, because it's just going to make you mad.

They're everywhere!
All those radios? That's a sale that Motorola isn't going to get. That's a sale that was in the bank in the past. School district needs 500 radios? That sale goes to Motorola. Business needs a dozen new radios? Motorola. Well....not anymore. The Big 3 are losing money every single day these CCRs are being sold in the US.