I suspect we’re all talking past one another.
Baggage claim for arrivals has to be outside the security cordon that applies to departing passengers being screened for weapons. For all the reasons @md-2000 said.
But that same baggage claim can also be walled off from the general public who might drive up to the curb. Thereby preventing random thieves from pulling up, entering bag claim, grabbing a suitcase at random, then driving off.
At most US airports this last form of security is not done. In general, at US airports anyone can walk up to the baggage carousels, grab any bag they want, and leave. Some US airports have a few “greeters” standing around watching the proceedings and will ask at least some people picking up bags to match their claim checks with the luggage tags. But that is pretty desultory at best and is pretty rarely deployed in general.
I’m going to bet that @FinsToTheLeft is talking about this latter situation which in other countries may be done more with walls, one-way exits, and other physical barriers than with half-assed claim check matching.
The other thing @FinsToTheLeft may be talking about is international arrivals. Which involve both immigration and customs and inspections on top of any security inspections.
The typical process when arriving internationally whether into the US or into Country X, is to first meet with an immigration official who’ll inspect your passport, visa, any immigration form they require arriving people to fill out, then stick all that info in their computer.
Assuming you pass that filter, you’ll move to a secure baggage claim area. But that movement is one-way; you’re not able to get back to the departure lounges from there. And nobody from the insecure public side of the airport can get into here either.
Once you have your checked baggage, then you, your checked baggage, and your carry-on baggage proceed to customs inspection. Where another official will “inspect” your possessions. And maybe all your paperwork again. With widely varying degrees of diligence, suspicion, and thoroughness.
Assuming you pass that scrutiny, you and all your possessions pass through another one-way exit into the general public area of that airport and can now mingle with the general populace of the country. But up to that point nobody of the general public can get back to where you and your baggage have been.
To be sure, there’s lots of local and regional variation in these processes.
Sometimes there’s a (usually desultory) security check after customs before you get into the general public. As in all baggage X-rayed, but only rather insensitive metal detectors for people, and maybe not even that. etc. I guess they’re looking for gun smugglers.
Sometimes there’s different screening and different movement flows for passengers just transiting through this airport in country X on the way from country A to country B. The various passport free zones for nationals of some countries but not all, such as Schengen in Europe, add more wrinkles to the mix.
But the bottom line is there are different sorts of “security” we can be talking about, and different levels of segregation of different flows of people and their possessions as they move through an airport whether departing, arriving, or both.