There are a number of good reasons to use a VPN:
It encrypts your activity on the web.
It hides your activity from anyone who might be interested in it.
It hides your location, enabling you to access geo-blocked content (e.g. on Netflix and other sites).
Makes you more anonymous on the web.
Helps you keep the connection protected when using a public WiFi hotspot.
Overall, use a VPN if your web privacy, security, and anonymity are important to you.