Because the solution is not something we can throw money at and expect a fast cure. Even cancer has the hope of a treatment that works in months to years. Climate change requires changing nearly everything about how we generate energy and requires us to find novel ways to remove greenhouse gases from the atmosphere. This latter bit can have money thrown at it, but without the former it's pointless. It'd be a cancer treatment while the patient huffs burning asbestos.
The difficulty in treating coupled with the fact that climate change is a slow process that wreaks havoc over years to decades means the short-term-focused economies and markets largely try to adapt to long-term changes instead of solving the issues. When you're only concerned with a few fiscal quarters at a time, why would you think on the scale of decades?