Kids are their own incentive. You only don't want kids because you don't believe you are capable of caring about another person more than you care about yourself. It's a life experience that, by missing out on, you deny yourself one of the main reasons for existing, and all the benefits and growth opportunities that come with it.
What is happening is you are being incentivized to depend on the government to take care of you in your old age. What will happen instead is you will be locked up in an old folks' home to die from neglect, alone, without anyone to care that you are gone.
The liberals who do have kids treat them like a fashion accessory, and use destroying their reproductive capabilities to advance their social standing rather than take the responsibility of having children seriously, so it's probably better that they don't have them.