This is not true in the UK. You are paid a tax free stipend (currently ~£14k) and not considered a full worker - you certainly don't have the rights that full time staff have.
There is no salary progression, bonus or pension and your funding cuts off at 3/3.5/4 years. After that, you aren't eligible for any govt. benefits as you are a full time student.
In some parts of the UK £14k can go a long way, but UK PhD students definitely aren't equal to full time staff as it stands.
The pay can be higher with industry partnerships (£30k tax free!!) but this is the more usual research council level.
I quit recently after 5 years. I don't think I regret it - the improvement in my mental health has been dramatic. I found it difficult to trust any of the advice I was getting from supervisors etc. because our interests weren't aligned.
I can say that I'm significantly more highly skilled than when I started though. Knowing that I didn't want to stay in academia, I spent a lot of time working on my transferable skills (i.e. tech).