In the US, you can be pretty much fired at a whim. You can fired for no reason at all(companies get in trouble when you get fired for a specific reason that they are not supposed too. Examples would be sex, age, or race for example).
The thing is, if a company that fires you does not have a good reason, the state will pay unemployment benefits. Where do they get the money from? They charge businesses a fee, depending on how many people they employ and how often they fire someone. Companies that have a habit of firing people are charged a higher fee because they are putting a burden on the state.
For leocharre here, he mentioned that the owner is an accountant which probably he knows the rules better than most people. If this guy is the penny-pincher that I think he is, then he is trying to avoid having to pay that higher fee. It is a petty thing, but there are plenty of petty people out there.