I'm no expert, so will be grateful if someone more knowledgeable (perhaps that's you @yonem, perhaps not) can fill in the gaps here as I'm puzzled by the net contributor, net recipient set up.
If you just take the tax and NI people pay, yes, I can see there might be a negative.
Does this 'net recipient' title take into account the fruits of the labour a person has put in over time. E.g. I worked 40 years before retiring. During those 40 years I created profit/value for my employer every hour I worked (I must have done otherwise they'd have made me redundant). My employers product/service generated tax, NI, VAT, employment for other people etc etc.
How about caring or childcare? People caring for loved ones, Grandparents caring for children - all frees up other people (who might not be able to work otherwise) to be in the labour market and pay tax etc.
Is that 'fruits of labour' element considered?