You can try it now, just activate an ad blocker.

It's a whole different world. I'm always amazed how many ads are on the webpages nowadays, when i use a machine, which is not mine and it has no ad blocker installed.
On a more serious note: Which was first? The ads or the ad blockers? No-one cared to make (or use) any ad blocker until the ads weren't intrusive to the point where they started to seriously and negatively affect the user experience.
You can thank the existence of ad blockers to greedy webmasters and advertisers, who taught text ads aren't enough, we need blingy, moving flash ads with annoying sound possibly stuffed with malware/adware and countless popup windows. That's what pisses most people off, if there were only text ads and other non-intrusive advertising, no-one would really care to use an ad blocker.