Let me guess, they watch them because they want to 'support the product' or ads are so high budget these days they're like 5 minute AAA movies?
No, most people really are so dumb when it comes to tech they can't install a browser extension. It's really terrifying considering how much of a focal point it's become in our lives.
There was this study back in 2016 that found under a third of the population in most rich western countries could handle a computer task more complicated than hitting reply all to an email. People like you and I and most people on sites like Kiwifarms or Reddit or 4chan have trouble comprehending this, but to them when we talk about something the slightest bit technical we sound like we're speaking pidgin to them.
A site like Reddit apparently has 234 unique visiters a month. That's 5% of the 4.57 billion people worldwide that use the internet. Think of the dumb people you've met on Reddit. They're still in the top third of people in terms of technical proficiency and very likely in the top 10%, because most people can't handle a computer task more complex than a single step and are not going to be able to figure out anything more complex than setting up a Facebook account where you basically just have to enter your personal information.
Your average, non-power or business user in 2020 accesses the internet on a mobile phone.
90% of that time is spent using apps to access online services. I doubt a huge chunk of people even know what a internet browser is, let alone what an extension is. Don't get me wrong, they use a browser on occasion, but if you asked them what browser they use they will look at you dumbfounded. They just touch the little icon on their phone and google things instead of typing in addresses. A large percentage of these blue-checkmarks you argue with on Twitter literally would not know how to access Twitter if you deleted the app from their phone.
There used to be this idea when I was in high school and me and my buddies would upgrade our Windows 98 desktop PCs and play Doom on the school's lan that one day everyone would be like us and know how to do these things. Nope. They just made computers dumber.