It's honestly both. Counters hurt more because you don't see them coming. That plus getting hit CLEAN by someone " going easy " hurts your ego a little bit. The person you're sparring with probably figured that they can raise the intensity if you're landing consistent counters on them. And imo, they SHOULD raise the intensity a bit. If you can continue landing your strikes under raised pressure, then you own the technique and they're going to keep eating punches. And if you can't, then you should be focusing on other parts of your game. Otherwise you're just flow sparring without a threat and while that does have a purpose, it's not everything.