In the US particularly, tipping is basically just making up for the fact that the person is underpaid. Plumbers are typically very well rewarded for the work they do - restaurant waiters, less so.
And it's this tacit admission that those workers are underpaid that makes this particularly embarrassing. We can generally agree these people are underpaid (we all generally tip and agree on the reasoning behind it) yet we can't agree to raise the minimum wage to get them a livable income.
Waiting tables and other tip-based compensatory jobs are specifically granted an exception to the minimum wage, so I don't think raising the minimum wage would change anything.
Depending on where you work and how experienced you are, waiting tables or bartending can be very lucrative relative to the amount of education or experience required to do the job. I'll certainly not suggest that a Denny's waiter or a Wal-Mart cashier are not underpaid, but grouping all waiters together and labeling them underpaid is an oversimplification.
Vox said it well with "consumers should not be responsible for paying the incomes of a restaurant owner's employees. "