I am sharing this because I think it's important and it's one of those rare things where we can make a direct and useful impact. So, I am taking the time to write this.
A while ago I read in a Facebook post that different restaurants have different policies about tips. Sometimes the policy is not to pass on the tips given by customers to the waiting staff.
Personally, I think that the tips are an important part of the waiting staff's income and the restaurant should not interfere or intercept them. But since reading that FB post I have started to ask every time I eat out and have been surprised to see many different policies.
Some places pass the whole amount to the waiting staff, some places do a percentage (ranging from 40% to 80%) and in some places it depends on the method of payment. For example, a place where we had lunch today, the waiting staff doesn't get any tips left by a customer if it's added in the card payment. If the tip is cash, they get all of it. Needless to say, I paid my bill by card but left the tip in cash.
The waiting staff cannot say this to the customer, it would be against the rules and will be unprofessional but if you ask them they will tell you freely what the exact policy is.
My take on the thing is that the waiting staff should get all their tips, the amount depends on the service as well as the customer's inclination, but they should get their tips, in most cases, it's considered part of their remuneration when the employer fixes their salaries.
From my side, the suggestion is that you ask your waiter/waitress about the tipping policy in the place when you are paying your bill, but of course you are free to do as you please. If you feel like this is worth sharing, feel free to forward it on FB or elsewhere. You don't need to link back or anything but I am happy if you do as well.
And a funny collection of tip jar pictures for your amusement: