The truth is that Adblock, Adblock plus and UBlock and every anti-ads plugins/software out there are not blocking ads, they are blocking your browser from accessing remove accessed content that are not hosted on the page nor server you're viewing.
There's an really easy way to keep advertisement on your website even for users who uses anti-ads plugins/software: Integrate your own advertisement system into your site archistructure and make it so that it's not loaded from an easy-to-guess link. For example, don't put every ads behind something like wikia.ads.XXXX as this is just too easy to guess. Instead, having something, having something like wikia.com/wiki/ASh2ahjksdh2 for the source of an add should not be blocked.
Now, the reason why almost nobody is doing this is because they don't want to invest in this methods while someone offers a easier and faster methods that can be blocked by anti-ads. They all use APIs that does everything automatically and that's the really bad thing to do.
There are 2 reasons why most started using Anti-Ads plugin/software:
1) Intrusive advertisement which destroy the user's experience from "pleasant" to "a real pain in the butt". Those includes ads that opens pop-up automatically, ads that enlarge, play a video or hide content on the page and even some that change the current page for another (those are the worse as you want to check some information and as the page load, it change to another unrelated page you never wanted to visit.)
2) Threatening advertisement which contains virus, trojan, key-loggers and even WIFI flash script. Basically, with the raise of the Online advertising popularity in the end of the 90's and early 00's, the companies that manages the ads in their servers (which are unrelated to the websites that use the API to load them remotely) started to make things a lot automatic. Instead of having a real person to check for an ads integrity and make sure it's not some scam or infected ads, they started to use bots to do the job. Some don't even uses bots, but instead do a primary scan with a Anti-virus which doesn't load and scan anything remotely accessible in the ads.
Those infected ads might not be numberous (like 0.01% of the ads stored), but whenever someone has that ads appearing and if it's well made it's one user that gets infected with crap that can really destroy his or her week... or even professional life depending on what has to be done with his/her PC afterward. That's like a bad lottery ticked that, when you win, you got some nasty PC diseases to fix or even have to pay someone else to fix. It's not even something that is related to the website you visit anymore, but instead related to the company that host the advertisement and that's something you can't check before it's too late. It's not like you got a warning on a page that tells you "Our ads are hosted by XXXX. Do you accept these or do you want ads hosted by another company?" That's because websites like wikia and pretty much every websites with high traffic rate in the world uses the Ads hosts that offers the best revenus over said traffics... even if it comes with a small risk for a small % of their users.
The only reason why websites couldn't make their own advertisement system integrated into their structure without using remote access to ads hosts is because their traffic would be too small to be able to attract companies to pay to have their ads displayed. That's not the case with websites like Wikia.com. There are companies that would be willing to pay a good amount to have their ads priorized and managed on the right Wikia's pages instead of just appearing randomly everywhere.