Not to ruin the absurdity of it, but sometimes they have "until supplies last" on digital promotions because they have a limit on the total number of redemptions.
In a case like this, I would assume it is a budgetary thing - if your marketing campaign is budgeted at $100k, you wouldn't want to give away a million dollars of free goods.
Basically the company is "losing" money every time someone claims the promotion because they are giving their service away for free.
Normally, companies will have a good estimate on how many people will make use of the promotion and how much money they will "lose", but sometimes the reality exceeds expectations and so they put a cap on tbe number of times a promotion can be claimed so as to not get exploited too much.
Btw I say "lose" in quotes because it may not be an actual loss of money but a loss of potential earnings from a customer. Also, don't worry about the downvotes, I've seen many innocuous comments also get a few downvotes for no reason.
I have a Walmart+ subscription, literally the only thing I'm subscribed to (beyond utilities or whatever).
Why?
I'm disabled, live off of only disability, my car got stolen.
Walmart accepts SNAP, and a + subscription gets you free, same day deliveries from your local store, as well as free 3 day shipping for something they retail but don't have in stock at the moment at your local store.
Very, very useful for groceries when you have no means to get to a grocery store.
A subscription costs a bit less than $15 bucks a month, and deliveries cost $10 bucks minimum each time otherwise.
... Had I a car, I'd hobble to food banks. But I don't, and am basically immobile, and still require food to not die.
...
You know all those meal kit delivery plans you see everyone advertising on their youtube videos?
Yeah, none of them (that I'm aware of) accept SNAP, even though they easily could, as they're not sending you hot food.
It's kinda stupid, for digital things it should be a line similar to "Limited time only", "While supplies last" has always been for physical deals where there's an actual limited quantity