A VPN provider can tell you they're not logging your traffic because they think they aren't but really they are because there's a box somewhere that your traffi

A VPN provider can tell you they're not logging your traffic because they think they aren't but really they are because there's a box somewhere that your traffic passes through that has logging enabled (for example -- and don't hyperfocus on the example, I know how you programmer types like to pick up the example and play ping pong with it for six hours). So incompetence is a reason to not trust a provider as well.