If an employer knows they have 1 person working, why schedule hordes of appointments?

Just tired and pi$$ed off about my employer, who once again, decided to leave me hanging my by myself on a busy Saturday. They knew they scheduled a ton of clients/customers/vendors to "stop by" for something. They knew I was alone. They knew all these people would likely come by at the same time. Why? Why do this to your loyal employees?

So glad I'm nearly out of here. Burnout is real.