Ha!
I'm a single parent and I earn just above minimum wage. I never tip. Why on earth would I actively seek to boost somebody else's wages when they are banking the same as I am each month, or probably more so with all their cash in hand tips? I think not. It is not my responsibility to top up wages - it's an employers. Dealing with the public is shit and I do it every day. I neither get, nor would expect any extra simply for doing my job. I knew what my work would be paying me per hour when I signed on the dotted line - just like everybody else. If you've got a problem with your wages, take it up with management, not paying customers.
I fail to see how my not tipping makes me tight, mean or socially inept 
I'm not about to bust my arse at work for a whole hour just so that I can give it away to the chap who bought me a plate of dinner from the kitchen whilst already getting paid to do so. It's completely illogical. I have to work a shit load of overtime and save like crazy to afford any small treats for myself and my dd. I refuse to just throw hard earned money and time spent away from my child away in such an outdated, grabby way.
And let me be clear - the reason I don't tip is not because I don't get tipped myself. I don't tip because we have a NMW here in the UK. I don't tip because I find the whole idea of it utterly moronic. I don't tip because the price I see set out in front of me is the price I expect to pay.
Let's put it into perspective shall, we?
You've just been served at a supermarket checkout. You could have sworn the total came to £30.00 but no, it's £34.50. You question it and the cashier politely responds, "15% service charge. See you again soon!"
You've just treated yourself in Topshop. You've already paid the cost of your new shoes plus VAT, but instead of paying £70.00 you paid £80.50. You walk back into the shop and question the girl at the tills, and she responds, "15% service charge. See you again soon!"
You've just handed your library books back in, relieved that they weren't late. The man at the desk is quietly scanning the books back into the system, but asks you to hold on before you shoot out the door to run some more errands. When he finally looks up at you, he nods his head towards a big glass jar sitting next to his potted indoor plant. It reads: 10% tip welcome.
You're frantic because your child's carer hasn't turned up today and you're now running late for work. When you finally get through to them on the phone and ask them where they are, they respond, "I quit. I've gone to work for another family. This one actually remembers to tip me."
The cleaners have just gone on strike at your place of work and to make matters worse, one of the toilets is now blocked. When you ask the reason for the strike, your boss explains they want "Equal tips for all workers!"
A little ridiculous, no?