You're ignoring opportunity costs, even in your meatworld analogy. There's real dangers to staying at home all the time, from social isolation to diseases of inactivity. Similarly, without using the web and visiting new sites, you're missing out on a lot of opportunity to communicate, learn, and yes, buy things. It may well be a lot
less safe to avoid those things in the longer term.
Personally I block ads because I value my attention higher than advertisers value it. There is always an adversarial function built into ads; the advertising wants your attention, if nothing else, while I am interested in maintaining my focus. For similar reasons, I disable auto-suggest in Google search, animated gifs in the browser, and I use flashblock in all browsers that support it.
Anything continuously animated on the page whatsoever - no matter whether it's an ad, a subscription div popup, a "read next article" popup link, or a sharing toolbar - I block them all with element hiding helpers.
Because the greatest risk to me in browsing a random site is getting distracted and sucked down some rabbit hole. I use all the tools at my disposal to eliminate visual distraction.