When you use a commercial VPN service, you share a server - and often an IP address - with hundreds or thousands of other users. This shared environment creates privacy risks: another user's illegal activity could attract law enforcement attention to a server carrying your traffic, and traffic analysis becomes easier when an adversary can observe the combined traffic patterns of many users on a single IP.
A private VPN server eliminates these risks entirely. Your server's IP address is used by you and only you. There are no other users whose activities could draw attention to your traffic. The encryption keys exist only on your server and your devices. No VPN company employee has access to your connection, and no other customer's compromise can affect your security.
Private VPN servers also deliver consistent performance because you never compete for bandwidth, CPU, or RAM with other users. During peak hours, when commercial VPN servers slow to a crawl under the load of thousands of users, your private server continues operating at full speed. The experience is like having your own private highway while everyone else sits in traffic.