>If people aren't going to be polite and accept that contract then fine, enforcement was always by an honour system.
No, it wasn't: it was on what I would call "the ignorance system". The vast majority of users were simply too lazy or ignorant to install ad-blockers. Ads made money because most users had no idea they could be blocked, or because the users just didn't care. Hang around non-technical people and talk to them about this and you'll see: many users just don't see what the big deal is, while others will admit to finding the ads annoying but don't even know it's possible to block them easily.
However, this is slowly changing, as 1) word spreads about ad-blockers, which isn't just word-of-mouth, but all these news articles lately probably help too, and 2) the ads get more and more annoying and intrusive. Remember how everyone wanted pop-up blockers 20 years ago when those became so popular with advertisers? It took a while there too, for word to get out about the ability to block pop-ups, but eventually it became the norm and was even built into browsers because the pop-ups were SO annoying and even destructive.
>But strategically if a service's social contract doesn't work for someone then they shouldn't use that service
Yes, they should, if they want to. Contracts require two parties to agree to something, and there is no such thing here. You can't just come up with a business model (e.g. pop-up ad supported website) and then claim there's a "social contract" in place when you just implemented this unilaterally.
The REAL social contract that's in place is the HTTP system the entire WWW is built on, where you send a request to a web server and it sends a response. What you do with the data you receive is up to you. It's absolutely no different than watching a TV show (in pre-DVR days) and then muting the volume or leaving the room when the commercials come on. Or better yet, in 2002 buying a DVR and just skipping the commercials.
You do have a point that a lot of services are funded by ads, and depend on enough people seeing these to sustain operations financially. But that's a business model chosen by these companies; they're free to choose a different business model if too many people start blocking ads. If people block ads, it's their own fault anyway, for making the ads too annoying. Back in the days of banner ads, almost no one cared about blocking them, because they just weren't that bad, just like no one really cared much about all the ads in newspapers. But that wasn't good enough for the advertisers. They brought ad-blocking on themselves by their own actions.