There is no "can't or won't" on a global scale: some countries have, others haven't as a function of their means. The fact that ultra wealthy individuals have better means than entire countries is an indictment of the state of affairs, not praise.

Edit: To elaborate on the above: eradicating polio isn't something that democratic, liberal countries are uniquely good at. Autocratic and despotic governments have also historically been good at it and have aggressively pursued it, because paralyzed citizens just aren't very useful. Countries that don't pursue eradication are historically ones that just lack the means (whether that's money, or infrastructure, or whatever), not ones with specific political structures.