I personally don't use VPN to stay anonymous simply because I don't trust that VPN company won't keep logs of who am I and of my activity.
Your ISP definitely keeps logs of everything you do, and they are linked to your real name and address. At least with good VPNs you can sign up anonymously and pay in anonymized bitcoin.
True. But I don't mind my ISP keeping track of what I do online. When I will mind that, I will use Tor browser to stay anonymous.
But the problem with anonymity is that you have to be very careful what you are doing when browsing anonymous. It takes one tiny mistake to disclose your identity. You can make 999 correct steps to avoid being identified and then you make one mistake (like entering your phone number or any other personal data) and your anonymity is gone...