We've debated around this several times in our team as well, as one can argue "it's just a number" and not really meaningful, but in short (sorry not that short really!):
The game started off as a small project where we added high-scores "for the sake of it" and because we like seeing it as a sort of "achievement" and comparison to others as well - believe it or not many of our players like the stats, and would even like to see more types of them. We also wanted to experiment with (yes you'll read this right) making idle games have meaningful competitions, that can reshape/shift the scales and keep things "competitive" for longer.
Currently we have "weekly competitions", that are based just on these numbers, but the rewards from them also help keep progression curve slightly up at later stages. And also, again a lot of our players like them!
So even if they may not be a core element of the gameplay, it still makes it as sort of an achievement and more interesting to many players.