My mom always said that I was a tougher child to raise than my sister. She understood how a little girl thinks, but she didn't understand the psychology of little boys at all. When I was a little kid I would do something that was obviously dumb, my mom would ask me "why did you do that?" and without fail I would say "because I wanted to know what would happen." This exasperated her to no end, because I probably knew what would happen beforehand, and my mom knew that I probably knew what would happen beforehand, so my answer didn't actually answer anything. Honestly, I don't know why she bothered asking. You either intuitively understand why someone would do something that was pointlessly destructive or you don't, but there's no logical explanation that could be given for that sort of behavior that would satisfy anyone.
Like a lot of older women, I don't think my mom will ever "get" a Jackass movie. I mean, yes, she can probably understand that kicking someone in the nuts can be funny, and she might understand why someone would bankroll a whole movie of non-stop nut shots, but there's a deeper existential question that she will never be able to understand. Which is: why do any of these men sign up for these stunts? Almost every single one of the skits in this movie has only one possible outcome: pain. You don't have to guess what will happen if you let a baby alligator bite your nipple. You aren't going to learn anything by snorting wasabe, especially on the third try. You can imagine what it's like to get a papercut on your tongue without actually doing it. But these guys continue to sign up for these endurance tests, even though there is nothing to learn from them. And since I am a former rambunctious boy and not my mother I have to say: God Bless them for it.
I can understand if someone just thinks these movies are juvenile, but I've always liked the rambunctious joy of the Jackass franchise. They scratch an itch I have for mayhem better than almost anything else I've come across. A lot of prank shows tip into cruelty pretty quickly, but Jackass is an insular enough world that for the most part the people that get pranked will be the ones pulling the prank later. That reciprocity matters a lot to me. I would probably find this more depressing than funny if these guys were hurting each other out of malice, but there is an obvious camaraderie on display, and most of the time the Jackasses delight in what's happening around them. When you combine those two factors you short circuit my empathy pathways and suddenly I feel fine with laughing at someone who just got kicked in the nuts.
There are a lot of good ways to defend the Jackass movies' technical merits. For one the editing is always right on point; every clip goes by quickly without wearing the joke into the ground, but the clips are also ordered so that they compliment each other instead of duplicating each other. They also have a knack for taking set ups that only have one possible outcome and twisting them so that they are surprising; the film rotates between skits which are one simple idea done simply, one simple idea that takes a dark turn, and more involved bits. But honestly there's no point in talking about the Jackass movies' legitimate merits, because you're either on board with a movie about riding a dirt bike into a pile of cacti or you aren't. Personally, I'm on board; I really loved the post-crash debate between the disgruntled stuntman and the camera crew about whether he was stuck in "cacti" or "cactuses". If you're my mom, on the other hand...