Well. I am going to be somewhat the voice of dissent (although not entirely). I think, like so many things in the horse world, the answer is “it depends”.
My personal experience is as follows: I have bought three horses for myself in my lifetime (I’m 30). I tend towards owning one riding mount at a time and that horse stays with me until it dies. I didn’t do a PPE on any of them. The first was a 19yo TB that I had leased for a while. I knew his limitations and so it didn’t feel necessary to me. I put him down at 31 after he wintered very poorly. My second was a yearling filly that I bought after I retired Horse #1. If I had done a PPE on her, it might have revealed the physical wreck she would become, but most likely not. I had to put her down at age 9 because of bilaterally fusing hocks and navicular in both front feet. Could I potentially have saved myself the heartache and financial losses? Maybe, hard to say. But even so, I wouldn’t change a thing - that mare ended up changing everything for me in terms of my horsemanship. I literally would not be who I am as a horseperson without her influence.
My third is my current gelding - this one was purchased by a student of mine who wanted an easy-going trail mount. He is a fantastic trail mount, for sure, but turned out to be too sensitive for her and with gaits that were difficult for her to ride. She asked me if I’d take him. I didn’t do a PPE on him, either. I knew him well and had had a hand in advancing his education. He has some “stuff” in the form of an old crush injury to his shoulder when he was much younger that resulted in some serious compensatory issues in his neck and poll. He’s taken quite a while to work through those and it’s something I address every ride with him. But I knew what I was taking on, he’s a joy to work with and again, he’s a horse that has demanded a level of horsemanship from me that has made me a better rider and handler.
People ride and thus buy horses for all kinds of reasons. It’s not up to me or anyone else to judge the worthiness of those reasons, although I have personal feelings about the integrity and morality of some of them.
So, for me anyway, the answer to “do I do a PPE” largely depends on why I want this horse, what my comfort level with “maintenance” issues is, and how educated I feel in terms of being able to spot potential problems. But I also don’t buy a horse off of one ride or one showing and I am a pretty educated rider and owner and thus I feel pretty confident taking on a wide range of “stuff” that might come up. I realize that is not the case for everything nor does everyone have the opportunity to get to know the horse a little (or a lot) before they buy them, so YMMV.
At the end of the day, buying horses is a balancing act. You can do everything right and still end up with a lemon, and you can pull a horse from an auction sight unseen and end up with a diamond in the rough. There are no guarantees. So I choose to go about it doing the best I can to balance my head and my heart, knowing that no matter what I am likely to get what I need.