Why leave bags at the front security desk? Meaning...

Why leave bags at the front security desk? Meaning/Purpose? This is 21st century. Install a scanning system if you doubt people might steal books out. Imagine how many times a person who stays the whole day in the library will have to go to the security room to collect and return the bag. I have never come across such meaningless restrictions anywhere... at least in US. Come South Australia. Adopt !!!!!