There are spammers and hackers everywhere on the internet. As people advertise to promote their business, so do websites. They track your identity when you visit them, with the help of your IP address and start sending you junk mails, ads and even spy ware that is hard to remove from your computer. There is the added danger of hackers and other cyber criminals. What a private proxy do is to stand like a wall between your vital data and these hackers. This adds to the security and privacy of your system.
There are other benefits of using these private proxies. For schools and offices, it is a must to restrict many sites from being opened by the students as the content of these sites is not suitable for viewing by children and the staff. The schools can send a list of such sites and many social networking sites to the proxy server which keeps on blocking any request that students may make in the browser. Any request to open a URL goes to the proxy server which opens it and then passes the information to your system which means that restricted sites never open in the system at the school.
But technological advances have found answer to this firewall also. There are many proxy servers that are free to use, and they allow students to bypass the filters that are being used by the school and then they are free to visit any site they want. Private proxy work both ways.