the secrets about library closing procedures

One day, I  found the answer to this question that had bothered me for ages:

Why do closing procedures in public buildings begin so early?

When the library closes at 9p.m. the closing procedure starts at 8.30 p.m. A first announcement warns that the library will be closing soon. Some guards even try to trick us by saying that the library will be closing in 25 minutes, while we still got 30. At 8.45 p.m, guards start addressing individuals.

My favourite guard walks through the halls repeating this one phrase like a mantra
“It’s time to pack up. If you are not packing up, by now, you should be packing up. If you’re not packing up you should be…”

Except from a handful of people the halls are emptying pretty quickly. I go through the reading hall, cross the exhibition space, trot down the stairs and under the stars into the bathroom.

As I walk into the bathroom, I instantaneously understand the hurry of all closing procedures: The bathroom is packed;
like at the cinema: as soon as the movie is over, the masses drain into the bathroom.

At exact 9.p.m I leave the building smiling to myself musing that I had finally found the most simple answer.