If you don’t use VPN all your traffic will flow through ISP. That doesn’t mean ISP can see your passwords or anything. They can only see which website you’re connecting to given that you are using unencrypted DNS if you are using encrypted DNS with TLS Hello they can only see IP. The claims that VPN protects you from hackers in public WiFi is dead since all websites switched to HTTPS and HSTS.

By using VPN all of these details now won’t be visible to your ISP but they will be visible to VPN provider.

If you live in a place where LEA can’t kick down your door and arrest you for visiting website it deems illegal then using VPN doesn’t give you anything.

Of course even a lot of first world country have strict laws against piracy in that case VPN is good but if you aren’t pirating and live in a free country I’d suggest don’t bother with VPN unless you have other reasons.Another reason could be to access geo restricted content on Netflix and stuff

Another thing to keep in mind, if you are committing/suspected of any crime then LEA will definitely go through your search history, they can get this through your device if you’ve cleaned that up but use google account then they can ask google, or go to ISP and ask this, obviously if you’re in this category then there are better solutions like Tor I2P

There are other extreme examples where a cheap ad friendly VPN with no registration comes in handy. If you want to create a zero knowledge email. Most email provider will block you if you are trying to create account with ProtonVPN or from Tor, but if your route your traffic through Tor and then to an ad friendly VPN they mostly allow it cuz they think you’re a dumb dumb. Note - it is generally not recommended to use VPN over Tor.