They know you use an ad-blocker and that you want to block ads, they don't know why, but they'll make an assumption. It is a fair guess that you use an ad-block

They know you use an ad-blocker and that you want to block ads, they don't know why, but they'll make an assumption. It is a fair guess that you use an ad-blocker because you don't want to see any ads; whether that is for privacy reasons, bandwidth, or because you dislike ads is not really relevant to them. In fact, most people who block ads probably do so for a combination of those reasons, and I am willing to bet that most users of ad-blockers simply don't want to see ads on every page they visit. So their assumption is not that unreasonable. If you want websites to know exactly why you use an ad-blocker, just mail them and tell them. The answer you'll receive (if any) will probably tell you that they depend on ad income to provide a free service, that they need ad delivery networks to act as brokers for their advertising space (and thus can't host their own ads), and that you are welcome to purchase a premium subscription if you want to use their service without ads.