I don't see why people are so incredulous about this. Honestly, when I hear this comment I assume someone is young or just jumping on the meme bandwagon (much like saying Taco Bell = diarrhea).
I'm a grown ass adult. Porn is cheap as shit. I'll pay for it because it's convenient, I can get exactly what I want, I can get it in very high quality, and I don't have to waste time or dig through and download anything potentially risky.
I pay for porn for much the same reason I use Steam. Maybe when was 18 or 20 and broke I'd pirate games and it would be a pain in the ass and sometimes they didn't work or needed workarounds. But Steam just makes it convenient. The games are cheap, I can get what I want, it's guaranteed to be quality, I don't have to waste time and don't have to dig through anything risky.
I'm an adult with disposable income. I pay for a lot of things because of convenience. I'll pay someone to mow my yard not because I can't, but because I don't have to. I'll pay for Netflix and Amazon Prime to have a lot of content available that I don't have to torrent. I'll pay for Youtube Red not because I want the premium content but just to avoid ads and use the play-in-the-backround feature on my phone. So obviously paying for porn is a no-brainer.
And with porn it's not like I'm a dinosaur who doesn't know how to use the internet. I'm plenty resourceful and spent plenty of time being resourceful growing up. But I just don't have to be. A $30 porn sub isn't going to break my bank account (and most mainstream stuff can be found for $10-15 with easily searched discounts).
I tend to stay subbed for a month, download a ton of content, then move on. I might hit 3-4 subs a year for one month each and just keep a lot of the content. Of course downloading porn is the other taboo amongst the 14-20 crowd. Look, my mommy isn't searching my browsing history. My wife isn't self-absorbed, insecure shrew who is going to give me shit. I keep my stuff nicely sorted and if she's like, "I'm really in the mood for Lexi Belle" or "got any hot Asians?" or "I feel like some soft, arty stuff" I've got it covered. It's easily accessible on the home network.
The only time I bother using incognito is when gift shopping.
I also find it interesting that as the internet has grown up, the consensus has become that you're a terrible person for pirating games, movies, or "TV" shows (unless they are impossible get and then it's fuck the corporations for making them unavailable). Everyone feels like the entertainment they and enjoy and those who create it should be paid so we keep getting great content. But for some reason that same rule doesn't apply to porn. I guess people like to think of those working in porn as subhuman and not-deserving for pay for their work. It's an odd bit of hypocrisy.