At least Kudos gives a writer some encouragement that their fic is being read.

But see this is like a conflicting set of ideas:
~ Writers want to know their stories are being read, so leave kudos to encourage...
~ But their stories could be being read and actually disliked...

Here's the thing: though it's really difficult (believe me, I know) writers on the whole need to develop tough skins and not expect encouragement at every turn.

Hope that doesn't sound callous, but it was a lesson I had to learn myself. Still have problems with it now and again, I admit, but I just think generic kudos really aren't something that is worth the effort.