As is frequently the case here, I feel most comments about whether or not to do a PhD are way too absorbed in cynicism and negativity.
Sure, a bad PI can make you miserable, and if you only catch on when you've already invested serious time into research, you might be stuck with that PI until you're done. But, at least from what I've seen at my university, you have a good amount of flexibility during the first years of the program. Plus, after the first semester, our department expects PhD students to do teaching assistant work if not funded by other means, which gives them the chance to work with professors without getting tied down to a PI, making it easier to make a more informed decision.
It's worth emphasizing that if you really love the topic, have confidence in your skills and can tolerate your PI, it can be a very fulfilling albeit stressful experience. My PI is typically well spoken, very demanding and often an asshole but also gives enough freedom and autonomy to grow. The pay is also definitely nowhere near as good as it would be in industry.
But as someone who would consider himself to have been pretty immature and mentally 'weak' (struggling to cope with anything stressful that wasn't an exam or project) when starting the program, I feel I have grown significantly as a person over the past few years in a way that would have likely involved a lot more exploitation and pain in industry (especially given my immigration status, which also tends to encourage exploitation). When I started, I struggled even with basic 'adult' things, yet 4 years in, approaching the end of my program, I am able to operate in the group mostly autonomously, with just occasional progress updates and handling basic decision making - reducing my PI's workload etc.
Additionally, as someone who had always been interested in physics, but pursued an education in computer engineering since that was my stronger skill, a PhD ended up giving me the chance to participate in cutting edge physics research despite my computer specialization.
I may have lost out on some wealth, but I feel I've more than made up for it through the personal growth, the satisfaction of unintentionally fulfilling a childhood dream, the satisfaction of making a measurable and meaningful contribution to science and the significantly expanded immigration opportunities compared to the conventional painful H1B->Green card route for Indians.
I can't speak too much about admissions, as my experience with that was fairly unusual - I transferred in from a Masters at the recommendation of the department chair with most other requirements waived because they remembered my classwork from undergrad and felt a PhD would fit me better. I was also set up with an introduction at a lab to fund me (granted that this did mean I didn't get any flexibility in choosing my PI). But I disagree with the general premise that PhDs are not worth it.