Today, we see a lot of places that have Internet access. And it is not about plugging up your laptop to cables. They are wireless. With that in mind all you need is a Bluetooth adapter that can detect these wireless networks. Normally you can surf away. But for some networks, there are codes that you have to input since not all air born Internet access is free for some places.
They would normally have a common username and password for people to use. Owing to the fact that they can make money from it or make it a privilege from patrons who avail of other services, wireless Internet is really more of an add-on. For others however, it is about security as well as routers in place can be susceptible to malicious files such as viruses which can be injected if some network administrators are not careful.
You really cannot blame such networks from employing such defensive security measures. At the rate that hackers and harmful files can be solicited over the web these days, safeguarding you equipment and files is a definite priority. Internet access through wireless technology is indeed a breakthrough but it also provides a threat for networks that are not careful on who can access them.
Hence, outside that of trying to control the number of devices accessing a network, it is a security measure to configure wireless networks and limit the ones who are given access. There is no telling what things may occur, and normally they are not favorable.