"If 15% pretax is still fairly "standard", then why do almost all restaurants include an 18% gratuity? Would not that indicate 18% might be a new standard? I generally receive more than either of those, but again, you said that is for standard service and I certainly aspire to be more than run-of-the-mill."

Perhaps so that they can continue tip escaleation to further escape having to pay labor a fair wage?

An industry does not set the standard price=that is not legal(especially something as voulantary as tipping)the consumer does.