I think it is more to try and have some amount of stability, rather than strictly how much you earn.

I used to live on £8k (part time apprenticeship), way below the poverty line apparently but I wasn't really worrying about money either.

Suppose it depends what you view poor as being. Some seem to view it as always being on the edge of running out of money at the end of each month. If that is the case then I wasn't poor despite only making £8k and I remember at the time hearing of people on over £25k who constantly were.

Even when I was on near minimum wage a couple years ago (£25k) I didn't really know what to spend all my money on. Honestly? I still don't. Picked up some hobbies but there is only so much you can spend gardening, a fork and spade don't cost that much and plants turn into more plants for free. Allotment rent is like £50/year.