I think the idea is that you will not necessarily choose near zero carbon alternatives such as cycling to work or buying an electric car. Those simply won't work for most for a variety of reasons. But by bumping the price of gas, it makes people who can't or won't choose an alternative very aware of the cost of going anywhere, and causes many to drive more sparingly by carpooling, waiting until they have multiple reasons for trips or choosing not to go out every weekend. For those with deep pockets it is probably little more than an annoyance that won't change their behaviour, but increasing fuel prices works very well to curb overall demand.