Sometimes you are not able to inform them of what is going on; it would be in very bad taste. And even the most excellent servers have a shift that goes wrong--or at the very least, a table. Any server who says they haven't are either 1) lying, 2) not realistic/not as good as they think, or 3) new. I know how much and how intensive that other work is.
I do not believe that tips are required; even if there is an auto-grat it is still not mandatory. I do, strongly, believe that you should work for those tips. But like I said, I was a greeter age 14-18, I waited tables from 18-21 (and did very well at it), I then managed from 21-25, and at 25 I went into restaurant consulting for several years. I was an event planner towards the end of that and after until my oldest was 2 ½. I still read the trades and do volunteer work within the industry and, occasionally still do consulting work.
In most circumstances I just can't bring myself to do it. Now, if the server does have a surly attitude and gives bad service, that is a different story. But basically, my big, dumb heart just can't bring myself to outright not leave a tip to some poor person making $2.13 an hour, tipping out on at least 8% of their sales, and usually giving away 3% of their sales to other people. 10% is punishment enough.
It's fine with me when anyone doesn't tip people who give bad service, even if tipped employees. Like I said, I do feel tips should be earned. I do not think that the gov't should allow tipped employees to make less than minimum wages. I just can't really do it myself. I know it's twisted, but it is what I do.