I've visited quite a few 10% "service" restaurants and I often leave a small tip on top of that because I'm entirely not sure whether waiters see any money from that "service".
The whole scheme is ridiculous: If you pay 18% for service, what are you paying the rest of 100% for? It doesn't make much sense. Just name your final price.
Isn't this a crazy sentiment though? It's like we've all been trained to pity waiters and unless we're handing them money directly we're worried they might go home empty handed. How did we get to this point?
If we weren't crazy on this part we would refuse paying anything not on the bill. Like we do in grocery store.
That being said, patrons are accustomed to paying an additional fee when dining out; so rather than simply raise prices (which I'm sure would elicit grumbling and/or loss of patronage), they maintained the expectation of paying an additional amount for the service they've received.
* I was going to call telcos an example, but then I don't know whether they don't already do that in the US. Or indeed anywhere. Which is a bit scary if you ask me.