If you have an ABS bike and do not keep your brakes in top order, there is always the possibility that one day, when you most need it, the ABS will not be there... only you will assume that it is and apply full braking effort....
Then, as you bounce down the road, you will know why looking after ABS brakes does become a little more critical, because on a non ABS bike you would not, or perhaps should not, apply full military braking effort in the wet, or even in the dry... because if you lock that front wheel....
An experienced rider would possibly know just how much pressure to apply to that front AND rear brake, but in the heat of the moment, you can overdo it that little bit lock the front and go bouncing down the road.....
We know this happens as we have read it on here more than once....
I also know of at least one rider whose ABS ceased functioning and apparently took the rest of the brakes off line with it.... don't know how and I actually don't think it was lack of maintenance... but it happened...
If your pistons are not moving back in and out as they should and the ABS tries to release the brake on that wheel, the brake may not come off....
Hopefully this explains what I was getting at because of course I never implied or even stated that the brakes on a NON ABS bike were any less important.... but you knew that... right?