Tipping is necessary if you want any hope of getting decent service.

With tips providing a chunk of their income, a server is way more likely to try and provide you with good service so that they are rewarded financially for their hard work.

Take tips out of the equation and they know they?re getting their money whether they provide excellent service or totally ignore you or provide shitty service. There?s no incentive for them to provide you with decent service and likely you aren?t going to get decent service.