An access point or router can send a steady stream of packets announcing that it is available for connection. A mobile phone or other device can usually see a list of nearby networks and will try to connect to one of them if access has been obtained before.
A network that is secured with a password will prevent most unauthorized users from accessing it. It's possible to completely disable the SSID broadcast and change the name to something difficult to guess. However, hackers can still retrieve an SSID from packets being transmitted. A password adds an extra layer of security. Individuals could benefit from turning off the SSID broadcast to keep neighbors or others from using their personal network. But businesses don't benefit much from doing it especially when they have a steady stream of customers wanting to access the guest Wi-Fi network.