No, the politicians expect to be out of office or dead by the time their commitments either come to pass or (more likely) it becomes clear those commitments will never work.

It's a shell game to them, and they have exit plans.

Do the politicians not plan on having grandchildren?

They probably don't plan on having poor grandchildren.

They expect to have grandchildren that are sufficiently powerful enough to choose their own geography.

When the glaciers in the Himalayas have melted they're going to be hurting for water.

The leaders' kids should be able to make it out to somewhere least impacted.

It's simple - the majority of the population lives in awful circumstances and to allow them to live in better conditions, you have to generate a lot of emissions.