Democrats still seem to feel as if they got a raw deal after the last census. Had they benefitted in any way, I’m pretty sure we wouldn’t be talking about this. This is all about them, not democracy.
Around the time of the last couple of censuses, they were pushing hard to base the census on a statistical sampling rather than an actual count. They can manipulate statistics to "show" that there are more traditionally Democrat constituents (e.g. homeless and welfare queens) than there really are--so they can then draw Democrat districts that contain fewer people than there really are. This way, they can get more representatives than their real numbers warrant.
The discipline of statistics was invented because it is impossible to count in every situation. It was not invented to bypass counting. Whenever it is possible to count, it is preferable to do so.