This is one thing I never understood, especially when people try to use them for small purchases. At my workplace, the store owner has disallowed us from accepting $50 and $100 bills in order to avoid having to check for counterfeits. People get very upset at this policy.
One time, a customer came up to the counter with the items they had picked out. I scanned them all up and then provided her with the total. She then tossed a $50 bill on the counter. I politely explained that due to store policy, I would be unable to accept it, so she'd have to either break the bill elsewhere, or she'd have to provide a different payment method.
In response, she snatched the bill off the counter and angrily said, "Well, I'm never shopping here again." She said this loudly enough that it took aback multiple nearby customers, who began to look on.
After digging in her purse, she tossed two smaller bills onto the counter, which turned out to not be enough to pay for the total (after the cash she still owed $7-8). I explained this to her, and then she snatched the cash off the counter and left. The next customer I interacted with, who had witnessed everything, told me that she'd "go easy on me". Haha.
I understand it can be frustrating to not be able to pay with the money you have on you in the moment, but I wish customers would understand that the store owner sets the policies, not the people working for the owner. Retail workers don't really have any power in that regard, we just work here. Also, I wish they'd understand we are not a bank; even if we did take larger bills, we don't have a million dollars in the register to give you. Usually, we have just enough to get through the week. It's just a nuisance.
Gas stations, convenience stores, and small businesses are common targets of scams and counterfeit currency. It's important to take that into account too as it relates to possible losses. Also, the fact that we just generally have less change available in our registers compared to larger businesses. It's not that uncommon to see locations like this refuse larger bills as a result. I fully understand being annoyed at this at big box / larger chain stores and businesses, of course.
It is currency and not very much money any more. If employees are incompetent, the job does not lay enough to attract qualified candidates. This is almost always the issue. Being cheap about labor is the real issue. Punishing the public for poor management is nonsense. This is why I would walk out. I instantly connect all the dots with my past experience. Stupid doesn't exist on a lonely island all buy itself. Seeing something so obvious means every underlying aspect of the business will be equally incompetent. This means I can do better on my own online without the overhead of a commercial storefront. I know exactly what a brick and mortar store has to offer above and beyond anything available online, but this kind of nonsense tells me that the person managing the back end is an idiot and is unlikely to provide any potential value. The real potential value is in quality control, unique products, and relationships. Creating any resistance with valid funds is asinine stupidity that makes all potential values in physical retail irrelevant. It really means the person behind the curtain is unstable, unreliable, or just not very bright.