was with my mil. She refuses not to leave anything.
Without wanting to be mean, she is the problem and just helps to endorse making terrible service the baseline for everybody. It's actually also very disrespectful to servers who do make a big effort to go above and beyond, as people like her won't (visibly) appreciate it - or does she tip good servers even more? What would be her maximum? Would she pay double or treble the bill for out-of-this-world amazing service?
Now that everybody earns at least minimum wage, the only sensible thing to do is to get rid of tipping completely. What's the betting that top-notch servers also have it used against them by exploitative employers, who tell them that, because they're so good, they can always earn more in tips, so they don't need the employer to pay what they're really worth?
It really is madness that a table of people who are all on minimum wage can go out to a restaurant for a special treat and are then expected to overpay their bill specifically because their server is 'only' on minimum wage. Even if they are all middle-aged and have to budget very carefully to run households and provide for children, whilst the server might be a young adult who lives bill-free with their parents and spends all of their earnings on expensive luxuries.
If the absurdity of tipping isn't clear to you, just stop to think how you'd react if you paid for your shopping at a till, in any supermarket, store or small shop, and when you paid by card, the machine prompted you to add a tip for the checkout assistant - maybe 'recommending' 10 or 15% - or actually went ahead and added the 10, 12.5, 15% as a 'service charge' and left it to you to ask for it to be removed if you spotted it and were brave enough to do so.
Or a plumber, or car mechanic, or bus driver, or childminder, or council worker if you pay your council tax over the counter; or ANY other industry/transaction except for a restaurant, takeaway, hairdresser or taxi driver.
Most people wouldn't just not accept it - they'd be outraged, screaming about what a disgusting rip-off scam it was and warning everybody they know to never do any business with them.