Not sure I can answer that. If there’s any kind of billing, they’d at least need to make sure the computer connecting to a tunnel is being used by a paying user. Mullvad does a privacy-minded token system for that, but it’s still a kind of login.
If you’re looking for private browsing without a login, you’ll want to use TOR.
Why do any VPNs require an account?
Not sure I can answer that. If there’s any kind of billing, they’d at least need to make sure the computer connecting to a tunnel is being used by a paying user. Mullvad does a privacy-minded token system for that, but it’s still a kind of login.
If you’re looking for private browsing without a login, you’ll want to use TOR.