To Tip or not to Tip

Why do I feel guilty that I didn't tip when the service was crap?

I hate when I go out to eat and the service was terrible and I still feel the need to tip.  I kind of get embarrassed when the waiter/waitress is staring at the same screen you are when you pass back the debit/credit device.  I shouldn't be embarrassed but I am.  I can't help it. I usually over tip because I feel for them.

I use to be a waitress for several years and I have to say I kind of expected a tip.  I only ever got $8/ hour plus tip so I really relied on those tips to get some money.

I felt that serving wasn't worth the money although some nights I brought home $230 a night plus my wage.  Everything about being a server was difficult.

I certainly respect them..  usually I respect them that is, until tonight.  I don't know why I got so offended when this waitress was rude to me.  She wasn't helpful at all.  Apparently she is on thin ice and soon to be fired as she excepts phone calls in the bathroom when she is waiting on tables.

I got the bill and I knew from that point that I had no intentions of giving her a tip.  She never asked if we wanted a refill or even cleaned up our plates.  One of the waitresses that I use to work with came over and kindly took our plates away and asked if we needed a desert menu.

Should I feel guilty that I didn't tip her anything?

It also makes me mad that some places include the gratuity into the bill.  What is with that?  What if I hate the service, would I have to pay anyway?

How do you feel about tips?