For me at least a part of it is a combination of general appreciation for good art and interesting concepts, and also a gradual desensitization to weird shit after years of exposure. A lot of really fun and creative (and horrifying) ideas can be found when you go digging through some of the darker stuff, provided that you have the stomach to handle it. A great example of this is id:1090599 (don't look if you're squeamish, btw). This one has some spectacular attention to the details of the anatomy that you might not otherwise see in more "traditional" porn. The cum on the roof of the mouth is absolutely delicious as well. "Reverse blowjob" is such a fun tag too.

Anon: Reverse blowjob, huh? How would that work exactly? Like...is it a giant sentient cock that's sucking on a person's head or something? *Looks at image* ...Ohhhhhh. I get it. Reverse blowjob. Cause it's going in from the other direction. Decapitation and such. Right, right...