Stop increasing child maintenance due to a paying parent earning more

I don’t get why just because the paying parents wage increases them the child maintenance increases. A child’s needs do not change regardless of a parents income. Some children do not receive any maintenance whilst others receive more then some adults monthly income. There should be a cap set per child and a set cap for more then one as people are still receiving the same on universal credit which doesn’t get effected regardless of what maintenance another parent gets. It doesn’t seem fair.