My eldest is 12.
It is absolutely unreasonable to assume that 12-15 year old children are safe left home alone for 5 days a week for a whole month.
Some families and children/young teens will have social and/or familial networks that can alleviate this type of isolation. Friends and known adults around who will share activities and care.
Some people live within communities where other children/youth are local, accessible by foot/cycling/public transport.
Some people have activities that aren't too expensive and which interest their children available locally too. Swimming pools, tennis courts, youth centres.
But some people don't have family available to provide care or company. No friends who are able/willing to fix things up. And no local facilities.
It's not just about childcare, I think most agree. It is about meaningful employment and appropriate supervision so that young people are safe - including safe from radicalisation, sexual predators online etc - and the responsibility cannot be just on the parent. Singular. And when it's singular it's usually the mother.
Not all work places will allow the same flexibility and many cannot afford to risk losing employment.
It's not unreasonable to be unhappy that a system of tax credits has changed.
And it is not unreasonable to want something to be available beyond programs for primary aged children and volunteer/work opportunities for older teens.