@kirbykirby you're skating dangerously close to pro-eugenics chat there. That the value of a person is wholly dependent on the financing they can offer a society and how independent they can be. That isn't just harmful to children who are born into families with generational trauma (which is the case for most families where they aren't working or seeking work), it's also highly ableist and potentially racist if you include unaccompanied minors or children who are seeking refugee status coming to the UK.
I'd also say you need to clarify what you mean in terms of who you're addressing? If you're addressing people who are economically inactive- then you rule out anyone who's on a job-seeking component of UC.
Which leaves you with the elderly, people with caring responsibilities, mothers who would otherwise be on maternity leave, those with long term health problems, the disabled or those in education. Do you think that all of those people are invaluable to society? At the end of the day, there needs to be a balance between ensuring that benefits are given appropriately to people who are genuine entitled to them, and in a way that doesn't become so invasive or inaccessible that people who are vulnerable struggle to access them independently and without support. I work with a number of young people who probably fall into your category of being a "financial/ social burden to the state" who are reasonably healthy but aren't working. All of them would like to work, they want a good quality of life for themselves, however, they don't have the social/personal skills to actually be ready to be in work and sustain work. Getting them to that point is a massive piece of work, and often a lot of them do go on and do work and do really well. But we are only working with small numbers very intensively, we have a massive waiting list. Without that support in place (often involving me physically going to work with them to teach them how to conduct themselves and get them past the initial period of learning the ropes and settling in that they otherwise don't have the resilience or confidence for) how would you expect them to get or sustain work?
Also just to add the majority of young people in work with want to go into caring professions and end up doing so, but if you don't have that funded and resourced support in place in the first instance- then you can't expect people to just get up and walk into a job tomorrow.
More people are vulnerable than you think but equally more vulnerable people are capable with the right support than you'd think. So your argument of only being valuable if you're going to be a net contributer is kind of pointless- noone has any way of knowing if a child from a neet family background is or isn't going to be a contributer. The government needs to have things in place to make work and education more accessible.