When you don't need a VPN
Why we wrote this
We give away a VPN, so this article runs against our immediate interest. We wrote it anyway, because recommending a tool for a problem it does not solve ends up hurting whoever trusted the recommendation.
On your home network, for ordinary use
If you browse from your own network, you already control the first stretch. A VPN there only changes who sees your domains: instead of your carrier, the VPN provider.
It can make sense if you would rather your carrier did not log it. But do not confuse that with added security: your home network does not become safer by using a VPN.
When the problem is something else
If you want to avoid advertising tracking, what you need is a browser that blocks trackers and good cookie hygiene. A VPN does not touch cookies.
If viruses worry you, you need a patched system and to avoid software of dubious origin. A VPN does not see the content of what you download.
If you fear someone getting into your accounts, the answer is two-factor authentication and unique passwords. A VPN does not protect an account whose password someone knows.
If your life depends on anonymity, you need Tor and training in operational security. A commercial VPN knows your real address.
When it can get in the way
Online banking. Many banks flag access from a VPN address as suspicious and block the session.
Services that forbid it in their terms. Some platforms close accounts over it. Worth checking.
Video calls. The detour adds latency, and in a long meeting you notice.
Captive portals. Hotel wifi will not load its sign-in screen if the VPN is already on when you connect.
So, where yes?
On networks you do not control, when travelling, when working outside the office, and when your network blocks services you need to reach.
Outside those cases, there is no harm in leaving it off. A tool used where it belongs is worth more than one left on out of habit.