Because it creates a Door to Hell https://en.wikipedia.org/wiki/Door_to_Hell
2) From an environmental standpoint, isn't CO2 in the atmosphere better than methane?
Lighting it would be admitting defeat. I suspect pride is a factor here.
Well... careful with estimates on that. From the Door to Hell article:
> It was estimated that the gas would burn out within a few weeks, but it has instead continued to burn for more than four decades.