Let's go straight to the point:
You obviously already know why ads are bad.
But let us remind you.
If you never experienced a huge feeling of rage growing while reading an article online, seeing parts of the page moving around, banners in the middle of the text, and even nasty popups with no "close" button, well, you're lucky.
Let's not even start with websites built only for clickbaiting, which links clog our social media pages.
This is why you are using an ad-blocker right now - and if you don't you really should.
Sometimes ads are just not appropriate.
Why, for a 20 second video, should we watch a 30 second ad? And, more on, in the middle of what you're watching?
If that's not enough for you...
Unfortunately yes, yes they are.
In the best possible scenario, companies that serve ads are just profiling you, and whatever you do online.
And let's be clear about what ad networks mean for "profiling":
They know which sites you visit, which products you bought in the past, which links you are more likely to click, and if you have a social account like facebook, twitter or instagram, how old are you, where you live and who your friends are.
Bad news is, if they wanted to, they could make your browser do whatever they want, even illegal activities, without you even notice.
Even worse, even if they don't want to, a breach in their security network can lead any hacker to easily inject malicious code inside the incredibly complex chain that brings one ad from the advertiser to your device.
Statistics say that people generally don't mind, or at least tolerate, advertisements, because they understand that it is a form of financing that allows them to avoid direct fees and usage costs.
What most people cannot tolerate, in every aspect of their lives, are invasions of their privacy and threats to their security, and current online ads do exactly that.
Tracking users with cookies is a normal practice, and the complex, uncontrolled, delivery chain permits any middle-system to inject any type of code in users' pages. This is where users' security and privacy are compromized.
The reasons for installing an ad-blocker are indeed very straightforward.
To anyone mildly interested in tech news, it will not come as a surprise that, instead of changing the existing technology, big advertisement companies are lobbying against ad-blocking practices and pushing browser creators to implement solutions which, in one way or another, will maintain the status quo.
Obviously having a trusty, clean and sustainable solution would be a better option.