I hate this argument; I go into a restaurant and expect to pay for some food that will be brought to my table by a waiter, that seems simple enough.
Why don't restaurants just work out how much this service will cost and make that the price charged rather than work out the cost less service then expect me to figure out the service cost. Does it cost more to carry a truffle from kitchen to table than a burger? No, so if you apply a strict percentage your either overpaying the truffle waiter or screwing the burger waiter. Should the waiter at Jo's diner get paid that much less than the guy at the Four Seasons?
Relying on or expecting tips is ludicrous, stupid even. Why take a job that pays less than minimum wage, I don't get it?
Basically, tipping is a mechanism for allocating a set amount of money, to be directly paid to the people who actually do the labour. It's not going to pay the electricity bill, or be taxed to the government, or go to the owner's son's college fund. Sure, it puts some responsibility in the client's hands, but that's what's necessary, legally, for this end-run to work.
Now, I'm sure you'll all say "why not just charge more for the food, and then pay them more?" Well, there's a couple reasons why. Most labour payment is by the hour, whereas tips are essentially a commission fee. Restaurants operate over a whole day, but tend to get most of their business during peak meal times. So it would actually be harder for a business to do hourly pay calculations than the inherently accurate tip commission. "Ok, so why don't they just raise prices, and pay the 'commission'?" Haha, well, there are several other factors. One being that it's a hidden rider cost, which means that psychologically people see a lower price, so they do business with you, and then pay the actual higher price. If they saw the higher price, they'd be more psychologically averse to entering into the transaction. Even though they're not being tricked, they know a tip is expected.
Also, a fixed commission doesn't really make sense. The reality is that people vary drastically in the amount they are willing to tip. Setting a fixed commission means that some will find it too high, and some would have gladly spent more. Why would a business choose to receive less money than they could? And why would they want to lose a complete transaction from someone who was willing to pay, just only a bit less? In this regard, it's not really the fault of the business that you're subjected to the tipping situation, it's your fellow consumers who create that market situation.
Also, certain waitresses/waiters create value, in the dining experience, themselves. A lot of men will specifically choose a restaurant because of the beauty of the waitresses. Or, people will come back, because a certain server treated them in a certain way. It doesn't really make sense to reward all serving employees, who create different levels of value for the customers and business, equally, when some are clearly doing a better job. Who should decide who gets what commission? In the end, the only fair arbiter would be the customer. Which is how tipping works now.
And that thing about the person carrying out a more expensive thing versus a less expensive thing, and the labour being equal, for a different economic return. Your looking at it from your perspective, as a single transaction. From their perspective, they have hundreds of transactions per day, and those kinds of labour/return differences all average out in the end. So, it might be relevant to you, but the $1 difference to them probably doesn't matter, compared to the $200 total sum.
And I hate to mention this, but I've noticed that a lot of people in the service industry get screwed by their employers for their fixed wages. A lot of places are mom & pop places which will probably go out of business in less than 2 years. Or even in larger places, the manager is probably an alcoholic, or is trying to take as much from the employees, for themselves, as possible. So, the competence and motives of management are questionable. Because of this, it's best for the staff to receive as much of their pay directly from the customer as possible. Tipping is the simplest means of accomplishing this. It's one thing to ask someone to change their method of business, but it's a whole new level of impossibility to ask a restaurant manager to acheive a new level of competence or fairness.
