The nation's health is affecting the economy massively. Fixing the NHS will have massive benefits to the economy even if they don't intentionally set out to do that. It's also a good way to sell the reforms.
The Tories wanted to privatise sick notes instead of getting people the care they needed to avoid being off work.
More people working also means more tax income.
As a parent of 4 kids I can safely say I would never leave them in a car in that heat. No matter the circumstances.