Here in the UK they do something similar at the casino I go to occasionally. I always assumed it was to do with money laundering (i.e. so they know exactly who everyone is at any one time in case of any suspicious betting), although I appreciate the law may be a bit different here.
In some European jurisdictions (I’m positive about Austria and most German states), it’s a legal requirement to ID casino guests. My assumption is that it’s for two reasons: (1) Money laundering; (2) check the guest’s name against blacklists (in European casinos, addictive gamblers can have their own name put on a blacklist to prevent themselves from playing, and the casino might be liable for compensation if they admit such players anyway). Apparently it’s not a legal requirement but rather a house rule in the OP’s case; my guess would be for blacklist check purposes, but it’s only a WAG.
Pennsylvania has finally updated some of their liquor laws, so I can buy beer and wine at some grocery and convenience stores. However, the cash registers are set up so that they cannot perform a sale without first scanning a drivers license and sending that information to the DMV.
I have purchased a six pack of beer, then decided to grab a second. Because my first transaction was closed out, I had to pull out my license for a second scan, even though my age had already been confirmed. It’s meant to be a fail safe.
I went to a Missouri casino a while back, and after checking my ID, the guy asked what year I was born. Trying, I suppose, to make sure I wasn’t using a fake ID. The thing is, a) there’s gray in my beard; even though (I’m certain) he’s legally required to check every ID, there’s no need to verify my age further. Which leads me to b) sure, I could have been a young person in costume faking my age, but I don’t see people going to such great lengths to get into casinos. To buy liquor, sure, but go to a casino???
I have seen ID checking fairly consistently in the Detroit casinos. I don’t go often but had a buddy turned away once, he was in gis 50s at the time.
I think that place like Vegas have much more advanced levels of security than the smaller markets. Better face detection, a larger pool of trained security personnel and agreements with other casinos to identified questionable players.
Why not? I don’t understand your confusion here. I certainly wanted to do anything I wasn’t allowed to do yet.
I just don’t believe that any teenager is that invested (to the point of putting on a disguse) in going to a casino, whereas many of them are so invested in buying liquor.
You’d be mistaken. My friends and I did when we were 20 (not to the point of a disguise). You know that you get served drinks in Vegas casinos, right?
The casinos may be using ID scanners like these, which are the ones used by the TSA when you go through the security checkpoint. The scanners detect “small discrepancies that TSA officers can’t see with the naked eye by comparing the scanned image to a document library with over 25,000 forms of identification.”

The casinos may be using ID scanners like these…
Yup, that is what they were using (at, at least, they looked like that).

Here in California, it’s legal for Target to sell beer and wine to anyone 21 years or older. They have apparently decided that it’s just easier to card everyone buying alcohol than to deal with the liability of letting any underage schnooks sneak through. So I’ve been carded there myself, gray and balding hair and old-age wrinkles notwithstanding.
Similarly, here in Ontario supermarkets can sell wine, and some of them have fairly large wine sections, though I think it’s mostly or entirely domestic. I bought some wine once at one store that I particularly remember because the cashier asked me for ID. I had a good chuckle because I thought it was a joke. It wasn’t.
My inference is that liquor stores, which are all government-run, train their employees to recognize underage would-be purchasers, or at least to be reasonable about not asking for ID if someone is ancient and decrepit and very obviously not underage, but the average supermarket cashier may not have a clue. So management was inconveniencing everyone in order to avoid any possible liability. Since casinos have an age requirement that could be another reason for carding everyone out of an abundance of caution.

So management was inconveniencing everyone in order to avoid any possible liability.
There was a bar in Chicago I went to a few times whose policy was to card absolutely everyone who entered. If Methuselah tried to get in they’d card him. This was their policy though, not something the government made them do.
The Walmart in Belleville ON has a beer and wine aisle. Only certain checkouts are set up to sell alcohol though; presumably these have any required document scanners plus trained personnel. I’m not sure; I’ve never been through those checkouts. On the rare occasions I go to Walmart, I tend to go through the self-checkout.

Only certain checkouts are set up to sell alcohol though; presumably these have any required document scanners plus trained personnel.
Also add in that they are staffed by someone old enough to sell alcohol. Many checkout clerks are teens and, if I go through their lane to buy alcohol, they have to call someone over who is old enough (over 21 in the US) to scan the liquor. Seems silly but it’s the law.
Drinking age is 19 here, but yes, I think the cashiers have to be old enough to use the stuff. Although, now that I think about it, I’m not sure why.
I’ve worked at many large corporations, like Target and grocery store chains. There are many advantages to having a “card every one” policy.
- it meets all legal requirements in every state.
- it’s easy to train cashiers (and to reprimand non-compliance).
- reduced temptation for cashiers when underage friends are buyers.
- reduced chance of discrimination complaints when every one is carded.
- increased compliance when customers see that every one is carded.
- even obvious seniors don’t object – most see it as humorous.
- list of all customers can be valuable to the business.
- can exclude ‘undesirable’ people (shoplifters, banned customers, etc.).
All these advantages easily outweigh the slight disadvantage of minor increased employee time.

The website about the program is blocked for me because I’m in Europe:
That link is mostly geared towards citizens who have questions about self-exclusion. It describes things like how to sign up for the list, how to get off of the list, whether you can add someone you’re concerned about to the list, etc.
The law surrounding the list is laid out in Part 3000 of the IL Administrative Code:
760(a) The Board shall maintain and keep current the Self-Exclusion List. The List shall be updated and distributed in its entirety to each riverboat casino on a regular basis.
…
770(a) No licensee shall knowingly allow any person placed on the Self-Exclusion List pursuant to Section 3000.750 to enter the area within the admission turnstiles of, or engage in gambling at, the riverboat gaming operation. …
(b) Owner licensees shall maintain, pursuant to Section 3000.760, a system designed to detect persons on the Self-Exclusion List so as to enforce this Part.
(As an aside, the code also says that “all references to riverboats in this Part apply to casinos and organization gaming facilities as well”; the above doesn’t just apply to literal boats.)
Not all states have self-exclusion lists like Illinois. In particular, this site (from a company that sells ID scanners to casinos) says that Nevada does not have a central self-exclusion program, though “individual casinos and gaming operators maintain their own programs”.
The last time I was in a casino was in Vegas about 4 years ago, and that didn’t happen. Is this a policy change across the board and, if so, why?
OP was in Illinois. No such thing exists in Vegas
Ah, okay, thanks!