The bag policy is actually pretty simple: it's all about keeping everyone safe and secure. You know how at the airport, they have those strict rules about what you can carry on? It's kind of like that, but way more relaxed. The Live Oak Pavilion just wants to make sure nobody brings in anything that could cause trouble.
For example, imagine you're at a concert, and someone in the crowd is carrying a huge backpack - it's a bit of a worry, right? You don't want anyone to get hurt, and neither does the Live Oak Pavilion. That's why they have rules about bag sizes and types.