This just shows the completely lack of financial understanding amongst people.
Firstly many people don't pay in at all.
Secondly even if you do work full time for say, forty years, that's not "your whole life." The vast majority of people spend half their life, at best working. So they still need to pay for the other half.
Finally even if you thought your "paying in half of your life" covers your "paying out" half - do YOU pay £250 a week of NI now? If you do you're in the top 1% of earners because someone on the average UK salary only pays £36 a week.
Tl;Dr- most people don't directly "pay in" anywhere near enough to accrue the amount currently being paid out as state pension.
Yes you might also think "but I cobtribute financially in other ways- tax, vat, council tax" - yep and that goes towards all the other services - roads, police, government, schools, nhs, defence funding, etc....and actually over the course of their lifetimes, most people don't pay in enough for what they receive there either.