Why do I need a subscription to use a VPN provider?

Basically because there are not VPN providers that offer you the possibility to enjoy that high level of privacy, security and connection speed for free.
Most VPN offer great deals at an affordable price, so anyone can go online safely and use a great connection for a reasonable price.
A lot of providers have a money-back guarantee for some period. In such way, you can try their services for a while and decide if that VPN services is the right one for you!