The thing to understand is that, until 2016, there was not one state pension, but two.
The basic state pension £141 a week, and a second, earnings related state pension.
If you worked in a job that had an occupational.pension, you played less NI but only built up entitlement to the basic state pension. When you retired, you would get this, and your occupational pension. You were "contracted ouf" of the second pension, but not the basic pension.
If you worked in a job that had no occupational pension, you paid more NI, but effectively got two state pensions once you retired.
Since 2016 there is only 1 state pension - the new state pension, which is worth £185 a week. The concept of being "contracted out" disappeared so people with occupation pensions started paying more national insurance.
I have just started getting my state pension. It consists of two parts. Pre 2016 I was paying contributions towards the basic state pension....£141. Post 2016 I was paying increased NI towards the new state pension.
I recieved £175 a week, which is more than I would have got under the pre 2016 scheme but less than the new state pension. So even though I had 44 years of contributions, I get less than the full pension, because I paid less NI for most of my working life. However, I also get an occupational pension which more than makes up the difference.