The basic problem is that attempting to mitigate this results in immediate financial costs, without providing any certainty of benefits. Even if there is some kind of benefit in the future, it will be difficult to ascribe it to the actions of the present. Business as usual provides an immediate benefit, and those that make these decisions can always hope that the future costs of climate change will be borne by a) people in other countries (perhaps those affected by rising sea levels) and b) people in the future, after the current bunch of politicians have retired.